Knowledge

Set cover problem

Source πŸ“

3081: 2992: 20: 1317:, with the universe represented by vertices on the left, the sets represented by vertices on the right, and edges representing the membership of elements to sets. The task is then to find a minimum cardinality subset of left-vertices that has a non-trivial intersection with each of the right-vertices, which is precisely the hitting set problem. 471:
is at least 1. The goal is to find a fractional set cover in which the sum of fractions is as small as possible. Note that a (usual) set cover is equivalent to a fractional set cover in which all fractions are either 0 or 1; therefore, the size of the smallest fractional cover is at most the size of
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for polynomial time approximation of set covering that chooses sets according to one rule: at each stage, choose the set that contains the largest number of uncovered elements. This method can be implemented in time linear in the sum of sizes of the input sets, using a
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is the problem of selecting a set of vertices (the dominating set) in a graph such that all other vertices are adjacent to at least one vertex in the dominating set. The Dominating set problem was shown to be NP complete through a reduction from Set
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problem, each set is assigned a positive weight (representing its cost), and the goal is to find a set cover with a smallest weight. The usual (unweighted) set cover corresponds to all sets having a weight of 1.
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Inapproximability results show that the greedy algorithm is essentially the best-possible polynomial time approximation algorithm for set cover up to lower order terms (see
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Information., Sandia National Laboratories. United States. Department of Energy. United States. Department of Energy. Office of Scientific and Technical (1999).
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problem, it is allowed to select fractions of sets, rather than entire sets. A fractional set cover is an assignment of a fraction (a number in ) to each set in
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below), under plausible complexity assumptions. A tighter analysis for the greedy algorithm shows that the approximation ratio is exactly
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is a computational problem equivalent to either listing all minimal hitting sets or listing all minimal set covers of a given set family.
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Gainer-Dewar, Andrew; Vera-Licona, Paola (2017), "The minimal hitting set generation problem: algorithms and computation",
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under the same assumptions, which essentially matches the approximation ratio achieved by the greedy algorithm.
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is described by a program identical to the one given above, except that the objective function to minimize is
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and the sets are induced by the intersection of the universe and geometric shapes (e.g., disks, rectangles).
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sets, then a solution can be found in polynomial time that approximates the optimum to within a factor of
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Karpinski, Marek; Zelikovsky, Alexander (1998), "Approximating dense cases of covering problems",
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Benchmarks with Hidden Optimum Solutions for Set Covering, Set Packing and Winner Determination
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But there is a fractional set cover of size 1.5, in which a 0.5 fraction of each set is taken.
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There is a standard example on which the greedy algorithm achieves an approximation ratio of
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Proceedings of the DIMACS Workshop on Network Design: Connectivity and Facilities Location
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showed that set covering cannot be approximated in polynomial time to within a factor of
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equals the universe, the set cover problem is to identify a smallest sub-collection of
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is the size of the set to be covered. In other words, it finds a covering that may be
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STOC '97: Proceedings of the twenty-ninth annual ACM symposium on Theory of computing
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is equal to 4, as there are four subsets that comprise this collection. The union of
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STOC '14: Proceedings of the forty-sixth annual ACM symposium on Theory of computing
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is to choose a set cover with no element included in more than one covering set.
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For a more compact representation of the covering constraint, one can define an
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showed optimal inapproximability by proving that it cannot be approximated to
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Proceedings of the thirty-third annual ACM symposium on Theory of computing
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the smallest cover, but may be smaller. For example, consider the universe
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Proceedings of the 25th International Workshop on Principles of Diagnosis
3622: 3372: 3167: 2502: 1324:, a hitting set for a collection of geometrical objects is also called a 524: 408: 400: 3956: 3881: 3080: 2991: 1135:
is described by a program identical to the one given above, except that
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is a special case of Set Cover when the universe is a set of points in
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A new multilayered PCP and the hardness of hypergraph vertex cover
3701:(1994), "On the hardness of approximating minimization problems", 3357:(August 1979), "A Greedy Heuristic for the Set-Covering Problem", 3175:
is to choose at most k sets to cover as many elements as possible.
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This greedy algorithm actually achieves an approximation ratio of
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This linear program belongs to the more general class of LPs for
412: 1556:{\displaystyle H(n)=\sum _{k=1}^{n}{\frac {1}{k}}\leq \ln {n}+1} 395:, and the task is to find a set cover that uses the fewest sets. 3542:(2006), "Algorithmic construction of sets for k-restrictions", 2486:{\displaystyle {\tfrac {1}{2}}\log _{2}{n}\approx 0.72\ln {n}} 1349:
to prioritize the sets. It achieves an approximation ratio of
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proved it is NP-hard to approximate set cover to better than
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using some polynomial-time method of solving linear programs.
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A compendium of NP optimization problems - Minimum Set Cover
3625:(1998), "A threshold of ln n for approximating set cover", 980:
otherwise. Then, the covering constraint can be written as
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in the universe, the sum of fractions of sets that contain
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proves that set cover instances with sets of size at most
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can be non-integer, so the last constraint is replaced by
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the integer linear program for weighted set cover stated
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is the size of the universe). It has been shown that its
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in 1972. The optimization/search version of set cover is
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Hitting set is an equivalent reformulation of Set Cover.
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of the greedy algorithm essentially tight in this case.
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is a certain constant, under the weaker assumption that
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Vertex cover might be hard to approximate to within 2βˆ’
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A tight analysis of the greedy algorithm for set cover
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respectively, as well as two additional disjoint sets
1273: 1247: 1219: 740:{\displaystyle \sum _{s\colon e\in s}x_{s}\geqslant 1} 229:{\displaystyle {\mathcal {C}}\subseteq {\mathcal {S}}} 3924: 3141: 3039: 2953: 2930: 2874: 2854: 2818: 2782: 2752: 2736:{\displaystyle {\bigl (}1-o(1){\bigr )}\cdot \ln {n}} 2686: 2658: 2635: 2612: 2578: 2561:{\displaystyle {\bigl (}1-o(1){\bigr )}\cdot \ln {n}} 2511: 2435: 2411: 2334: 2297: 2252: 2164: 2131: 2104: 2077: 2031: 2025:. On this input, the greedy algorithm takes the sets 2004: 1964: 1913: 1867: 1847: 1796: 1749: 1708: 1677: 1654: 1634: 1607: 1571: 1486: 1462: 1433: 1404: 1384: 1355: 1272: 1246: 1218: 1168: 1141: 1105: 1078: 1065:{\displaystyle \sum _{s\in {\mathcal {S}}}w_{s}x_{s}} 1021: 986: 946: 905: 883: 840: 793: 755: 698: 640: 445: 361: 334: 314: 274: 242: 208: 180: 156: 132: 3673: 3530: 3392: 2673: 3930: 3156: 3060: 2971: 2936: 2913: 2860: 2830: 2800: 2758: 2735: 2664: 2641: 2618: 2598: 2560: 2485: 2417: 2344: 2316: 2283: 2215: 2143: 2117: 2090: 2063: 2017: 1990: 1950: 1899: 1853: 1833: 1782: 1720: 1694: 1663: 1640: 1620: 1593: 1555: 1468: 1448: 1419: 1390: 1370: 1286: 1254: 1232: 1193: 1154: 1121: 1091: 1064: 1001: 971: 930: 889: 856: 824: 771: 739: 673: 455: 387: 340: 320: 300: 252: 228: 190: 166: 142: 3812:Combinatorial Optimization: Theory and Algorithms 2356:, then it becomes a (non-integer) linear program 4003: 2216:{\displaystyle \ln {n}-\ln {\ln {n}}+\Theta (1)} 674:{\displaystyle \sum _{s\in {\mathcal {S}}}x_{s}} 2868:cannot be approximated to a factor better than 388:{\displaystyle ({\mathcal {U}},{\mathcal {S}})} 301:{\displaystyle ({\mathcal {U}},{\mathcal {S}})} 3693: 2914:{\displaystyle \ln \Delta -O(\ln \ln \Delta )} 2426: 2155: 867:(every set is either in the set cover or not) 2714: 2689: 2539: 2514: 2360:. The algorithm can be described as follows: 613: 594: 486:The smallest set cover has a size of 2, e.g. 3827: 3767: 3447: 2677: 2400: 2278: 2266: 819: 807: 23:Example of an instance of set cover problem. 3271:"Fast stabbing of boxes in high dimensions" 3856:: CS1 maint: location missing publisher ( 3806: 3220: 2652:. A similar result with a higher value of 1304: 601: 587: 3907: 3716: 3640: 3555: 3488: 3289: 3144: 2839: 1671:dense instances, however, there exists a 1427:times as large as the minimum one, where 3951: 3780: 3741: 3435: 3423: 3256: 3244: 3232: 2845: 2569: 2226: 1730: 399:The decision version of set covering is 97:= { {1, 2, 3}, {2, 4}, {3, 4}, {4, 5} }. 18: 3353: 3268: 3071: 1297:for the minimum set cover problem. See 4004: 781:(cover every element of the universe) 3621: 2982: 2379:for which the corresponding variable 1841:elements. The set system consists of 3476:SIAM Journal on Discrete Mathematics 3075: 2986: 2505:(1998) improved this lower bound to 2425:refers to the size of the universe, 2352:in the integer linear program shown 85:For example, consider the universe, 3111: 2947:, thus making the approximation of 2674:Alon, Moshkovitz & Safra (2006) 2064:{\displaystyle S_{k},\ldots ,S_{1}} 1951:{\displaystyle 2,4,8,\ldots ,2^{k}} 1900:{\displaystyle S_{1},\ldots ,S_{k}} 1702:-approximation algorithm for every 1335: 1287:{\displaystyle \scriptstyle \log n} 1233:{\displaystyle \scriptstyle \log n} 1122:{\displaystyle s\in {\mathcal {S}}} 857:{\displaystyle s\in {\mathcal {S}}} 772:{\displaystyle e\in {\mathcal {U}}} 622:can be formulated as the following 13: 3828:Cardoso, Nuno; Abreu, Rui (2014), 3454:. United States. Dept. of Energy. 3360:Mathematics of Operations Research 2960: 2905: 2881: 2855: 2337: 2231:If each element occurs in at most 2201: 2125:. An example of such an input for 1628:is the maximum cardinality set of 1613: 1583: 1309:Set covering is equivalent to the 1114: 1035: 849: 764: 654: 448: 377: 367: 290: 280: 245: 221: 211: 183: 159: 135: 82:whose union equals the universe. 16:Classical problem in combinatorics 14: 4043: 3985: 3451:On the Red-Blue Set Cover Problem 3123:is a special case of Hitting Set. 2812:is true, this can be improved to 1194:{\displaystyle 0\leq x_{s}\leq 1} 62:, (henceforth referred to as the 3157:{\displaystyle \mathbb {R} ^{d}} 3079: 2990: 2284:{\displaystyle x_{S}\in \{0,1\}} 825:{\displaystyle x_{s}\in \{0,1\}} 126:More formally, given a universe 3466: 3441: 3429: 3417: 3393:Karpinski & Zelikovsky 1998 3129:is a special case of Set Cover. 3397: 3386: 3347: 3306: 3262: 3250: 3238: 3226: 3055: 3043: 2908: 2890: 2709: 2703: 2599:{\displaystyle c\cdot \ln {n}} 2534: 2528: 2345:{\displaystyle {\mathcal {S}}} 2210: 2204: 1820: 1808: 1783:{\displaystyle \log _{2}(n)/2} 1769: 1763: 1594:{\displaystyle H(s^{\prime })} 1588: 1575: 1496: 1490: 1443: 1437: 1414: 1408: 1365: 1359: 1255:{\displaystyle \scriptstyle n} 939:if element e is in set s, and 685:(minimize the number of sets) 497:Covering/packing-problem pairs 456:{\displaystyle {\mathcal {S}}} 405:Karp's 21 NP-complete problems 382: 362: 295: 275: 253:{\displaystyle {\mathcal {U}}} 191:{\displaystyle {\mathcal {U}}} 167:{\displaystyle {\mathcal {S}}} 143:{\displaystyle {\mathcal {U}}} 1: 3524: 3291:10.1016/S0304-3975(98)00336-3 3269:Nielsen, Frank (2000-09-06). 2972:{\displaystyle \ln \Delta +1} 2801:{\displaystyle f-1-\epsilon } 2572:established a lower bound of 1834:{\displaystyle n=2^{(k+1)}-2} 1002:{\displaystyle Ax\geqslant 1} 484:= { {1, 2}, {2, 3}, {3, 1} }. 463:, such that for each element 3328:(2009) , "Exercise 35.3-3", 3278:Theoretical Computer Science 2427:Lund & Yannakakis (1994) 1301:for a detailed explanation. 1299:randomized rounding#setcover 7: 2831:{\displaystyle f-\epsilon } 2317:{\displaystyle x_{S}\geq 0} 1991:{\displaystyle T_{0},T_{1}} 1790:. The universe consists of 1621:{\displaystyle s^{\prime }} 479:and the collection of sets 422: 92:and the collection of sets 31:is a classical question in 10: 4048: 3946:10.1016/j.jcss.2007.06.019 3606:Introduction to Algorithms 3407:. STOC'96, Pages 435-441, 3331:Introduction to Algorithms 2772:In low-frequency systems, 2678:Dinur & Steurer (2013) 2151:is pictured on the right. 614:Linear program formulation 3931:{\displaystyle \epsilon } 3753:, ACM, pp. 475–484, 3061:{\displaystyle O(\log n)} 2401:Inapproximability results 2364:Find an optimal solution 2156:Inapproximability results 972:{\displaystyle A_{e,s}=0} 931:{\displaystyle A_{e,s}=1} 4027:Approximation algorithms 3814:(5 ed.), Springer, 3787:Approximation Algorithms 3207: 3173:Maximum coverage problem 1861:pairwise disjoint sets 1695:{\displaystyle c\ln {m}} 1664:{\displaystyle \delta -} 417:approximation algorithms 3775:, ACM, pp. 624–633 3566:10.1145/1150334.1150336 2861:{\displaystyle \Delta } 2840:Khot & Regev (2008) 2810:Unique games conjecture 2672:was recently proved by 1305:Hitting set formulation 1295:approximation algorithm 549:Maximum independent set 236:of sets whose union is 3932: 3810:; Vygen, Jens (2012), 3221:Korte & Vygen 2012 3158: 3062: 2973: 2938: 2915: 2862: 2832: 2802: 2760: 2737: 2666: 2643: 2642:{\displaystyle \not =} 2620: 2600: 2570:Raz & Safra (1997) 2562: 2487: 2419: 2346: 2318: 2285: 2217: 2145: 2119: 2092: 2065: 2019: 1992: 1952: 1901: 1855: 1835: 1784: 1740: 1735:Tight example for the 1722: 1721:{\displaystyle c>0} 1696: 1665: 1642: 1622: 1595: 1557: 1522: 1470: 1450: 1421: 1392: 1372: 1322:computational geometry 1288: 1266:indeed gives a factor- 1256: 1234: 1212:of the ILP is at most 1195: 1156: 1123: 1093: 1066: 1003: 973: 932: 891: 858: 826: 773: 741: 675: 624:integer linear program 457: 389: 355:, the input is a pair 342: 322: 302: 268:, the input is a pair 254: 230: 192: 168: 144: 113:{ {1, 2, 3}, {4, 5} }‍ 24: 3969:10.1145/380752.380839 3933: 3892:10.1145/780542.780629 3870:Guruswami, Venkatesan 3718:10.1145/185675.306789 3651:10.1145/285055.285059 3594:Leiserson, Charles E. 3544:ACM Trans. Algorithms 3413:10.1145/237814.237991 3318:Leiserson, Charles E. 3159: 3063: 2974: 2939: 2916: 2863: 2833: 2803: 2761: 2738: 2667: 2644: 2621: 2601: 2563: 2499:quasi-polynomial time 2488: 2420: 2388:has value at least 1/ 2347: 2319: 2286: 2227:Low-frequency systems 2218: 2146: 2120: 2118:{\displaystyle T_{1}} 2093: 2091:{\displaystyle T_{0}} 2066: 2020: 2018:{\displaystyle S_{i}} 1993: 1953: 1902: 1856: 1836: 1785: 1734: 1723: 1697: 1666: 1643: 1623: 1596: 1558: 1502: 1471: 1451: 1422: 1393: 1373: 1289: 1257: 1235: 1196: 1157: 1155:{\displaystyle x_{s}} 1124: 1099:is the weight of set 1094: 1092:{\displaystyle w_{s}} 1067: 1004: 974: 933: 892: 859: 827: 774: 742: 676: 458: 390: 343: 323: 303: 255: 231: 193: 169: 145: 22: 4017:NP-complete problems 3922: 3845:10.5281/zenodo.10037 3373:10.1287/moor.4.3.233 3201:Monotone dualization 3139: 3072:Fractional set cover 3037: 2951: 2928: 2872: 2852: 2816: 2780: 2750: 2684: 2656: 2633: 2610: 2576: 2509: 2433: 2409: 2332: 2295: 2250: 2162: 2129: 2102: 2075: 2029: 2002: 1962: 1911: 1865: 1845: 1794: 1747: 1706: 1675: 1652: 1632: 1605: 1569: 1484: 1460: 1449:{\displaystyle H(n)} 1431: 1420:{\displaystyle H(n)} 1402: 1382: 1371:{\displaystyle H(s)} 1353: 1270: 1244: 1216: 1166: 1139: 1133:Fractional set cover 1103: 1076: 1019: 984: 944: 903: 881: 838: 791: 753: 696: 638: 544:Minimum vertex cover 443: 437:fractional set cover 359: 353:optimization problem 332: 312: 272: 240: 206: 178: 154: 130: 3793:, Springer-Verlag, 3699:Yannakakis, Mihalis 3426:, pp. 118–119) 3259:, pp. 110–112) 3195:Set-cover abduction 3191:Red-blue set cover. 3186:Exact cover problem 3133:Geometric set cover 3031:randomized rounding 2774:Dinur et al. (2003) 2144:{\displaystyle k=3} 1311:hitting set problem 525:Maximum set packing 488:{ {1, 2}, {2, 3} }. 41:operations research 4022:Linear programming 3928: 3782:Vazirani, Vijay V. 3704:Journal of the ACM 3628:Journal of the ACM 3499:10.1137/15M1055024 3154: 3091:. You can help by 3058: 3002:. You can help by 2983:Weighted set cover 2969: 2934: 2911: 2858: 2828: 2798: 2756: 2733: 2662: 2639: 2616: 2596: 2558: 2483: 2446: 2415: 2342: 2314: 2281: 2246:If the constraint 2213: 2141: 2115: 2088: 2061: 2015: 1988: 1948: 1897: 1851: 1831: 1780: 1741: 1718: 1692: 1661: 1638: 1618: 1591: 1553: 1466: 1446: 1417: 1388: 1368: 1284: 1283: 1252: 1251: 1230: 1229: 1191: 1152: 1119: 1089: 1062: 1041: 1013:Weighted set cover 999: 969: 928: 887: 854: 822: 769: 737: 720: 671: 660: 532:Minimum edge cover 453: 429:weighted set cover 385: 338: 318: 298: 250: 226: 188: 164: 140: 25: 4032:Covering problems 3839:, Graz, Austria, 3821:978-3-642-24487-2 3800:978-3-540-65367-7 3760:978-0-89791-888-6 3615:978-0-262-03293-3 3598:Rivest, Ronald L. 3590:Cormen, Thomas H. 3322:Rivest, Ronald L. 3314:Cormen, Thomas H. 3109: 3108: 3020: 3019: 2937:{\displaystyle =} 2759:{\displaystyle =} 2665:{\displaystyle c} 2619:{\displaystyle c} 2445: 2418:{\displaystyle n} 1854:{\displaystyle k} 1641:{\displaystyle S} 1531: 1469:{\displaystyle n} 1391:{\displaystyle s} 1206:covering problems 1022: 890:{\displaystyle A} 871: 870: 699: 641: 620:set cover problem 611: 610: 578: 577: 573:Rectangle packing 520:Minimum set cover 508:Covering problems 351:In the set cover 341:{\displaystyle k} 321:{\displaystyle k} 264:In the set cover 99:In this example, 90:= {1, 2, 3, 4, 5} 45:complexity theory 29:set cover problem 4039: 4012:Families of sets 3981: 3948: 3937: 3935: 3934: 3929: 3904: 3861: 3855: 3847: 3834: 3824: 3803: 3792: 3776: 3763: 3737: 3720: 3690: 3669: 3644: 3618: 3584: 3559: 3536:Moshkovitz, Dana 3518: 3517: 3492: 3470: 3464: 3463: 3445: 3439: 3433: 3427: 3421: 3415: 3401: 3395: 3390: 3384: 3383: 3351: 3345: 3344: 3310: 3304: 3303: 3293: 3275: 3266: 3260: 3254: 3248: 3242: 3236: 3230: 3224: 3218: 3163: 3161: 3160: 3155: 3153: 3152: 3147: 3112:Related problems 3104: 3101: 3083: 3076: 3067: 3065: 3064: 3059: 3015: 3012: 2994: 2987: 2978: 2976: 2975: 2970: 2943: 2941: 2940: 2935: 2920: 2918: 2917: 2912: 2867: 2865: 2864: 2859: 2837: 2835: 2834: 2829: 2807: 2805: 2804: 2799: 2765: 2763: 2762: 2757: 2742: 2740: 2739: 2734: 2732: 2718: 2717: 2693: 2692: 2671: 2669: 2668: 2663: 2648: 2646: 2645: 2640: 2625: 2623: 2622: 2617: 2605: 2603: 2602: 2597: 2595: 2567: 2565: 2564: 2559: 2557: 2543: 2542: 2518: 2517: 2492: 2490: 2489: 2484: 2482: 2465: 2457: 2456: 2447: 2438: 2424: 2422: 2421: 2416: 2392:in the solution 2368:for the program 2351: 2349: 2348: 2343: 2341: 2340: 2323: 2321: 2320: 2315: 2307: 2306: 2290: 2288: 2287: 2282: 2262: 2261: 2222: 2220: 2219: 2214: 2197: 2196: 2175: 2150: 2148: 2147: 2142: 2124: 2122: 2121: 2116: 2114: 2113: 2097: 2095: 2094: 2089: 2087: 2086: 2070: 2068: 2067: 2062: 2060: 2059: 2041: 2040: 2024: 2022: 2021: 2016: 2014: 2013: 1997: 1995: 1994: 1989: 1987: 1986: 1974: 1973: 1957: 1955: 1954: 1949: 1947: 1946: 1906: 1904: 1903: 1898: 1896: 1895: 1877: 1876: 1860: 1858: 1857: 1852: 1840: 1838: 1837: 1832: 1824: 1823: 1789: 1787: 1786: 1781: 1776: 1759: 1758: 1737:greedy algorithm 1727: 1725: 1724: 1719: 1701: 1699: 1698: 1693: 1691: 1670: 1668: 1667: 1662: 1647: 1645: 1644: 1639: 1627: 1625: 1624: 1619: 1617: 1616: 1600: 1598: 1597: 1592: 1587: 1586: 1562: 1560: 1559: 1554: 1546: 1532: 1524: 1521: 1516: 1475: 1473: 1472: 1467: 1455: 1453: 1452: 1447: 1426: 1424: 1423: 1418: 1397: 1395: 1394: 1389: 1377: 1375: 1374: 1369: 1342:greedy algorithm 1336:Greedy algorithm 1320:In the field of 1293: 1291: 1290: 1285: 1261: 1259: 1258: 1253: 1239: 1237: 1236: 1231: 1200: 1198: 1197: 1192: 1184: 1183: 1161: 1159: 1158: 1153: 1151: 1150: 1128: 1126: 1125: 1120: 1118: 1117: 1098: 1096: 1095: 1090: 1088: 1087: 1071: 1069: 1068: 1063: 1061: 1060: 1051: 1050: 1040: 1039: 1038: 1008: 1006: 1005: 1000: 978: 976: 975: 970: 962: 961: 937: 935: 934: 929: 921: 920: 896: 894: 893: 888: 875:incidence matrix 863: 861: 860: 855: 853: 852: 831: 829: 828: 823: 803: 802: 778: 776: 775: 770: 768: 767: 746: 744: 743: 738: 730: 729: 719: 680: 678: 677: 672: 670: 669: 659: 658: 657: 629: 628: 603: 596: 589: 568:Polygon covering 537:Maximum matching 513:Packing problems 504: 503: 493: 492: 489: 485: 478: 462: 460: 459: 454: 452: 451: 394: 392: 391: 386: 381: 380: 371: 370: 347: 345: 344: 339: 327: 325: 324: 319: 307: 305: 304: 299: 294: 293: 284: 283: 266:decision problem 259: 257: 256: 251: 249: 248: 235: 233: 232: 227: 225: 224: 215: 214: 197: 195: 194: 189: 187: 186: 173: 171: 170: 165: 163: 162: 149: 147: 146: 141: 139: 138: 122: 118: 114: 110: 106: 102: 98: 91: 81: 73: 69: 61: 37:computer science 4047: 4046: 4042: 4041: 4040: 4038: 4037: 4036: 4002: 4001: 3988: 3979: 3923: 3920: 3919: 3902: 3849: 3848: 3832: 3822: 3808:Korte, Bernhard 3801: 3790: 3761: 3688: 3616: 3602:Stein, Clifford 3557:10.1.1.138.8682 3527: 3522: 3521: 3471: 3467: 3446: 3442: 3434: 3430: 3422: 3418: 3402: 3398: 3391: 3387: 3352: 3348: 3342: 3326:Stein, Clifford 3311: 3307: 3273: 3267: 3263: 3255: 3251: 3243: 3239: 3231: 3227: 3219: 3215: 3210: 3148: 3143: 3142: 3140: 3137: 3136: 3114: 3105: 3099: 3096: 3089:needs expansion 3074: 3038: 3035: 3034: 3016: 3010: 3007: 3000:needs expansion 2985: 2952: 2949: 2948: 2929: 2926: 2925: 2873: 2870: 2869: 2853: 2850: 2849: 2846:Trevisan (2001) 2817: 2814: 2813: 2781: 2778: 2777: 2751: 2748: 2747: 2728: 2713: 2712: 2688: 2687: 2685: 2682: 2681: 2657: 2654: 2653: 2634: 2631: 2630: 2611: 2608: 2607: 2591: 2577: 2574: 2573: 2553: 2538: 2537: 2513: 2512: 2510: 2507: 2506: 2478: 2461: 2452: 2448: 2436: 2434: 2431: 2430: 2410: 2407: 2406: 2403: 2395: 2391: 2387: 2386: 2382: 2378: 2371: 2367: 2359: 2336: 2335: 2333: 2330: 2329: 2327: 2302: 2298: 2296: 2293: 2292: 2291:is replaced by 2257: 2253: 2251: 2248: 2247: 2238: 2234: 2229: 2192: 2185: 2171: 2163: 2160: 2159: 2130: 2127: 2126: 2109: 2105: 2103: 2100: 2099: 2082: 2078: 2076: 2073: 2072: 2055: 2051: 2036: 2032: 2030: 2027: 2026: 2009: 2005: 2003: 2000: 1999: 1982: 1978: 1969: 1965: 1963: 1960: 1959: 1942: 1938: 1912: 1909: 1908: 1891: 1887: 1872: 1868: 1866: 1863: 1862: 1846: 1843: 1842: 1807: 1803: 1795: 1792: 1791: 1772: 1754: 1750: 1748: 1745: 1744: 1707: 1704: 1703: 1687: 1676: 1673: 1672: 1653: 1650: 1649: 1633: 1630: 1629: 1612: 1608: 1606: 1603: 1602: 1582: 1578: 1570: 1567: 1566: 1542: 1523: 1517: 1506: 1485: 1482: 1481: 1478:harmonic number 1461: 1458: 1457: 1432: 1429: 1428: 1403: 1400: 1399: 1383: 1380: 1379: 1354: 1351: 1350: 1338: 1315:bipartite graph 1307: 1271: 1268: 1267: 1245: 1242: 1241: 1217: 1214: 1213: 1210:integrality gap 1179: 1175: 1167: 1164: 1163: 1146: 1142: 1140: 1137: 1136: 1113: 1112: 1104: 1101: 1100: 1083: 1079: 1077: 1074: 1073: 1056: 1052: 1046: 1042: 1034: 1033: 1026: 1020: 1017: 1016: 985: 982: 981: 951: 947: 945: 942: 941: 910: 906: 904: 901: 900: 882: 879: 878: 848: 847: 839: 836: 835: 798: 794: 792: 789: 788: 763: 762: 754: 751: 750: 725: 721: 703: 697: 694: 693: 665: 661: 653: 652: 645: 639: 636: 635: 616: 607: 487: 480: 473: 447: 446: 444: 441: 440: 425: 403:. It is one of 376: 375: 366: 365: 360: 357: 356: 333: 330: 329: 313: 310: 309: 308:and an integer 289: 288: 279: 278: 273: 270: 269: 244: 243: 241: 238: 237: 220: 219: 210: 209: 207: 204: 203: 202:is a subfamily 182: 181: 179: 176: 175: 158: 157: 155: 152: 151: 134: 133: 131: 128: 127: 120: 116: 112: 108: 104: 100: 93: 86: 79: 71: 67: 55: 17: 12: 11: 5: 4045: 4035: 4034: 4029: 4024: 4019: 4014: 4000: 3999: 3994: 3987: 3986:External links 3984: 3983: 3982: 3977: 3953:Trevisan, Luca 3949: 3927: 3905: 3900: 3862: 3825: 3820: 3804: 3799: 3778: 3765: 3759: 3739: 3711:(5): 960–981, 3691: 3686: 3671: 3642:10.1.1.70.5014 3635:(4): 634–652, 3619: 3614: 3586: 3550:(2): 153–177, 3526: 3523: 3520: 3519: 3465: 3440: 3436:Vazirani (2001 3428: 3424:Vazirani (2001 3416: 3396: 3385: 3367:(3): 233–235, 3346: 3340: 3305: 3261: 3257:Vazirani (2001 3249: 3247:, p. 108) 3245:Vazirani (2001 3237: 3233:Vazirani (2001 3225: 3223:, p. 414. 3212: 3211: 3209: 3206: 3205: 3204: 3198: 3192: 3189: 3183: 3179:Dominating set 3176: 3170: 3165: 3151: 3146: 3130: 3124: 3118: 3113: 3110: 3107: 3106: 3100:September 2023 3086: 3084: 3073: 3070: 3057: 3054: 3051: 3048: 3045: 3042: 3029:, one may use 3018: 3017: 2997: 2995: 2984: 2981: 2968: 2965: 2962: 2959: 2956: 2933: 2910: 2907: 2904: 2901: 2898: 2895: 2892: 2889: 2886: 2883: 2880: 2877: 2857: 2827: 2824: 2821: 2797: 2794: 2791: 2788: 2785: 2755: 2731: 2727: 2724: 2721: 2716: 2711: 2708: 2705: 2702: 2699: 2696: 2691: 2661: 2638: 2615: 2594: 2590: 2587: 2584: 2581: 2556: 2552: 2549: 2546: 2541: 2536: 2533: 2530: 2527: 2524: 2521: 2516: 2481: 2477: 2474: 2471: 2468: 2464: 2460: 2455: 2451: 2444: 2441: 2414: 2402: 2399: 2398: 2397: 2393: 2389: 2384: 2383: 2380: 2376: 2375:Pick all sets 2373: 2369: 2365: 2357: 2339: 2325: 2313: 2310: 2305: 2301: 2280: 2277: 2274: 2271: 2268: 2265: 2260: 2256: 2236: 2232: 2228: 2225: 2212: 2209: 2206: 2203: 2200: 2195: 2191: 2188: 2184: 2181: 2178: 2174: 2170: 2167: 2140: 2137: 2134: 2112: 2108: 2085: 2081: 2058: 2054: 2050: 2047: 2044: 2039: 2035: 2012: 2008: 1985: 1981: 1977: 1972: 1968: 1945: 1941: 1937: 1934: 1931: 1928: 1925: 1922: 1919: 1916: 1894: 1890: 1886: 1883: 1880: 1875: 1871: 1850: 1830: 1827: 1822: 1819: 1816: 1813: 1810: 1806: 1802: 1799: 1779: 1775: 1771: 1768: 1765: 1762: 1757: 1753: 1717: 1714: 1711: 1690: 1686: 1683: 1680: 1660: 1657: 1637: 1615: 1611: 1590: 1585: 1581: 1577: 1574: 1552: 1549: 1545: 1541: 1538: 1535: 1530: 1527: 1520: 1515: 1512: 1509: 1505: 1501: 1498: 1495: 1492: 1489: 1465: 1445: 1442: 1439: 1436: 1416: 1413: 1410: 1407: 1387: 1367: 1364: 1361: 1358: 1337: 1334: 1306: 1303: 1282: 1279: 1276: 1250: 1228: 1225: 1222: 1190: 1187: 1182: 1178: 1174: 1171: 1149: 1145: 1116: 1111: 1108: 1086: 1082: 1059: 1055: 1049: 1045: 1037: 1032: 1029: 1025: 998: 995: 992: 989: 968: 965: 960: 957: 954: 950: 927: 924: 919: 916: 913: 909: 886: 869: 868: 865: 851: 846: 843: 832: 821: 818: 815: 812: 809: 806: 801: 797: 786: 783: 782: 779: 766: 761: 758: 747: 736: 733: 728: 724: 718: 715: 712: 709: 706: 702: 691: 687: 686: 683: 681: 668: 664: 656: 651: 648: 644: 633: 615: 612: 609: 608: 606: 605: 598: 591: 583: 580: 579: 576: 575: 570: 564: 563: 558: 552: 551: 546: 540: 539: 534: 528: 527: 522: 516: 515: 510: 500: 499: 450: 424: 421: 397: 396: 384: 379: 374: 369: 364: 349: 337: 317: 297: 292: 287: 282: 277: 247: 223: 218: 213: 185: 174:of subsets of 161: 137: 74:subsets whose 15: 9: 6: 4: 3: 2: 4044: 4033: 4030: 4028: 4025: 4023: 4020: 4018: 4015: 4013: 4010: 4009: 4007: 3998: 3995: 3993: 3990: 3989: 3980: 3978:1-58113-349-9 3974: 3970: 3966: 3962: 3958: 3954: 3950: 3947: 3943: 3939: 3938: 3925: 3914: 3910: 3909:Khot, Subhash 3906: 3903: 3897: 3893: 3889: 3885: 3884: 3879: 3875: 3874:Khot, Subhash 3871: 3867: 3863: 3859: 3853: 3846: 3842: 3838: 3831: 3826: 3823: 3817: 3813: 3809: 3805: 3802: 3796: 3789: 3788: 3783: 3779: 3774: 3770: 3766: 3762: 3756: 3752: 3748: 3747:Safra, Shmuel 3744: 3740: 3736: 3732: 3728: 3724: 3719: 3714: 3710: 3706: 3705: 3700: 3696: 3695:Lund, Carsten 3692: 3689: 3687:9780821870846 3683: 3679: 3678: 3672: 3668: 3664: 3660: 3656: 3652: 3648: 3643: 3638: 3634: 3630: 3629: 3624: 3620: 3617: 3611: 3607: 3603: 3599: 3595: 3591: 3587: 3583: 3579: 3575: 3571: 3567: 3563: 3558: 3553: 3549: 3545: 3541: 3540:Safra, Shmuel 3537: 3533: 3529: 3528: 3516: 3512: 3508: 3504: 3500: 3496: 3491: 3486: 3483:(1): 63–100, 3482: 3478: 3477: 3469: 3461: 3457: 3453: 3452: 3444: 3438:, Chapter 14) 3437: 3432: 3425: 3420: 3414: 3410: 3406: 3403:SlavΓ­k Petr 3400: 3394: 3389: 3382: 3378: 3374: 3370: 3366: 3362: 3361: 3356: 3350: 3343: 3341:0-262-03384-4 3337: 3333: 3332: 3327: 3323: 3319: 3315: 3309: 3301: 3297: 3292: 3287: 3283: 3279: 3272: 3265: 3258: 3253: 3246: 3241: 3235:, p. 15) 3234: 3229: 3222: 3217: 3213: 3202: 3199: 3196: 3193: 3190: 3187: 3184: 3180: 3177: 3174: 3171: 3169: 3166: 3149: 3134: 3131: 3128: 3125: 3122: 3119: 3116: 3115: 3103: 3094: 3090: 3087:This section 3085: 3082: 3078: 3077: 3069: 3052: 3049: 3046: 3040: 3032: 3028: 3024: 3014: 3011:November 2017 3005: 3001: 2998:This section 2996: 2993: 2989: 2988: 2980: 2966: 2963: 2957: 2954: 2946: 2931: 2924: 2902: 2899: 2896: 2893: 2887: 2884: 2878: 2875: 2847: 2843: 2841: 2838:as proven by 2825: 2822: 2819: 2811: 2795: 2792: 2789: 2786: 2783: 2775: 2770: 2768: 2753: 2746: 2729: 2725: 2722: 2719: 2706: 2700: 2697: 2694: 2679: 2675: 2659: 2651: 2636: 2629: 2613: 2592: 2588: 2585: 2582: 2579: 2571: 2554: 2550: 2547: 2544: 2531: 2525: 2522: 2519: 2504: 2500: 2496: 2479: 2475: 2472: 2469: 2466: 2462: 2458: 2453: 2449: 2442: 2439: 2428: 2412: 2374: 2363: 2362: 2361: 2355: 2311: 2308: 2303: 2299: 2275: 2272: 2269: 2263: 2258: 2254: 2244: 2242: 2241:LP relaxation 2224: 2207: 2198: 2193: 2189: 2186: 2182: 2179: 2176: 2172: 2168: 2165: 2157: 2152: 2138: 2135: 2132: 2110: 2106: 2083: 2079: 2056: 2052: 2048: 2045: 2042: 2037: 2033: 2010: 2006: 1983: 1979: 1975: 1970: 1966: 1943: 1939: 1935: 1932: 1929: 1926: 1923: 1920: 1917: 1914: 1892: 1888: 1884: 1881: 1878: 1873: 1869: 1848: 1828: 1825: 1817: 1814: 1811: 1804: 1800: 1797: 1777: 1773: 1766: 1760: 1755: 1751: 1738: 1733: 1729: 1715: 1712: 1709: 1688: 1684: 1681: 1678: 1658: 1655: 1635: 1609: 1579: 1572: 1563: 1550: 1547: 1543: 1539: 1536: 1533: 1528: 1525: 1518: 1513: 1510: 1507: 1503: 1499: 1493: 1487: 1479: 1463: 1440: 1434: 1411: 1405: 1385: 1362: 1356: 1348: 1343: 1333: 1331: 1327: 1323: 1318: 1316: 1312: 1302: 1300: 1296: 1280: 1277: 1274: 1265: 1248: 1226: 1223: 1220: 1211: 1207: 1202: 1188: 1185: 1180: 1176: 1172: 1169: 1147: 1143: 1134: 1130: 1109: 1106: 1084: 1080: 1057: 1053: 1047: 1043: 1030: 1027: 1023: 1014: 1010: 996: 993: 990: 987: 979: 966: 963: 958: 955: 952: 948: 938: 925: 922: 917: 914: 911: 907: 897: 884: 876: 866: 844: 841: 833: 816: 813: 810: 804: 799: 795: 787: 785: 784: 780: 759: 756: 748: 734: 731: 726: 722: 716: 713: 710: 707: 704: 700: 692: 689: 688: 684: 682: 666: 662: 649: 646: 642: 634: 631: 630: 627: 625: 621: 604: 599: 597: 592: 590: 585: 584: 582: 581: 574: 571: 569: 566: 565: 562: 559: 557: 554: 553: 550: 547: 545: 542: 541: 538: 535: 533: 530: 529: 526: 523: 521: 518: 517: 514: 511: 509: 506: 505: 502: 501: 498: 495: 494: 491: 483: 476: 470: 466: 438: 433: 430: 420: 418: 414: 410: 406: 402: 372: 354: 350: 335: 315: 285: 267: 263: 262: 261: 216: 201: 150:and a family 124: 96: 89: 83: 77: 70:, of a given 65: 59: 53: 48: 46: 42: 38: 34: 33:combinatorics 30: 21: 3960: 3917: 3882: 3836: 3811: 3786: 3772: 3750: 3708: 3702: 3676: 3632: 3626: 3623:Feige, Uriel 3605: 3547: 3543: 3480: 3474: 3468: 3450: 3443: 3431: 3419: 3399: 3388: 3364: 3358: 3349: 3330: 3308: 3284:(1): 53–72. 3281: 3277: 3264: 3252: 3240: 3228: 3216: 3121:Vertex cover 3097: 3093:adding to it 3088: 3021: 3008: 3004:adding to it 2999: 2944: 2922: 2844: 2771: 2766: 2744: 2649: 2627: 2501:algorithms. 2494: 2404: 2245: 2230: 2153: 1742: 1564: 1347:bucket queue 1339: 1330:piercing set 1329: 1326:stabbing set 1325: 1319: 1310: 1308: 1203: 1132: 1131: 1012: 1011: 940: 899: 877: 872: 619: 617: 556:Bin covering 519: 481: 474: 468: 464: 436: 434: 428: 426: 407:shown to be 398: 199: 125: 123:has size 2. 107:is equal to 94: 87: 84: 57: 54:of elements 49: 28: 26: 3913:Regev, Oded 3878:Regev, Oded 3866:Dinur, Irit 3769:Dinur, Irit 3355:Chvatal, V. 3168:Set packing 1907:with sizes 1340:There is a 690:subject to 561:Bin packing 477:= {1, 2, 3} 409:NP-complete 401:NP-complete 4006:Categories 3901:1581136749 3532:Alon, Noga 3525:References 3490:1601.02939 3127:Edge cover 3033:to get an 1264:relaxation 56:{1, 2, …, 3926:ϵ 3727:0004-5411 3659:0004-5411 3637:CiteSeerX 3574:1549-6325 3552:CiteSeerX 3300:0304-3975 3050:⁡ 2961:Δ 2958:⁡ 2906:Δ 2903:⁡ 2897:⁡ 2885:− 2882:Δ 2879:⁡ 2856:Δ 2826:ϵ 2823:− 2808:. If the 2796:ϵ 2793:− 2787:− 2726:⁡ 2720:⋅ 2698:− 2589:⁡ 2583:⋅ 2551:⁡ 2545:⋅ 2523:− 2493:, unless 2476:⁡ 2467:≈ 2459:⁡ 2309:≥ 2264:∈ 2202:Θ 2190:⁡ 2183:⁡ 2177:− 2169:⁡ 2046:… 1933:… 1882:… 1826:− 1761:⁡ 1685:⁡ 1659:− 1656:δ 1614:′ 1584:′ 1540:⁡ 1534:≤ 1504:∑ 1278:⁡ 1224:⁡ 1186:≤ 1173:≤ 1110:∈ 1031:∈ 1024:∑ 994:⩾ 845:∈ 805:∈ 760:∈ 732:⩾ 714:∈ 708:: 701:∑ 650:∈ 643:∑ 632:minimize 217:⊆ 200:set cover 3955:(2001), 3915:(2008), 3880:(2003), 3852:citation 3784:(2001), 3743:Raz, Ran 3667:52827488 3604:(2001), 3582:11922650 3460:68396743 3023:Relaxing 2637:≠ 2606:, where 2324:for all 1739:with k=3 1378:, where 1072:, where 834:for all 749:for all 423:Variants 348:or less. 64:universe 50:Given a 3735:9021065 3515:9240467 3507:3590650 3381:3689577 2921:unless 2743:unless 1456:is the 1240:(where 626:(ILP). 435:In the 427:In the 413:NP-hard 3975:  3898:  3818:  3797:  3757:  3733:  3725:  3684:  3665:  3657:  3639:  3612:  3580:  3572:  3554:  3513:  3505:  3458:  3379:  3338:  3298:  3182:cover. 2239:using 1648:. For 1601:where 43:, and 3833:(PDF) 3791:(PDF) 3731:S2CID 3663:S2CID 3578:S2CID 3511:S2CID 3485:arXiv 3377:JSTOR 3274:(PDF) 3208:Notes 3027:above 2503:Feige 2405:When 2354:above 76:union 3973:ISBN 3896:ISBN 3858:link 3816:ISBN 3795:ISBN 3755:ISBN 3723:ISSN 3682:ISBN 3655:ISSN 3610:ISBN 3570:ISSN 3456:OCLC 3336:ISBN 3296:ISSN 2497:has 2470:0.72 2098:and 1713:> 1476:-th 618:The 198:, a 119:and 47:. 27:The 3965:doi 3942:doi 3888:doi 3841:doi 3713:doi 3647:doi 3562:doi 3495:doi 3409:doi 3369:doi 3286:doi 3282:246 3095:. 3047:log 3006:. 2450:log 2328:in 1752:log 1328:or 1275:log 1221:log 260:. 52:set 4008:: 3971:, 3959:, 3911:; 3894:, 3876:; 3872:; 3868:; 3854:}} 3850:{{ 3835:, 3745:; 3729:, 3721:, 3709:41 3707:, 3697:; 3661:, 3653:, 3645:, 3633:45 3631:, 3600:; 3596:; 3592:; 3576:, 3568:, 3560:, 3546:, 3538:; 3534:; 3509:, 3503:MR 3501:, 3493:, 3481:31 3479:, 3375:, 3363:, 3324:; 3320:; 3316:; 3294:. 3280:. 3276:. 2955:ln 2945:NP 2900:ln 2894:ln 2876:ln 2842:. 2769:. 2767:NP 2723:ln 2676:. 2650:NP 2586:ln 2548:ln 2495:NP 2473:ln 2243:. 2223:. 2187:ln 2180:ln 2166:ln 1728:. 1682:ln 1537:ln 1480:: 1332:. 1201:. 1129:. 1009:. 864:. 419:. 60:} 39:, 35:, 3967:: 3944:: 3890:: 3860:) 3843:: 3777:. 3764:. 3738:. 3715:: 3670:. 3649:: 3585:. 3564:: 3548:2 3497:: 3487:: 3462:. 3411:: 3371:: 3365:4 3302:. 3288:: 3197:. 3150:d 3145:R 3102:) 3098:( 3056:) 3053:n 3044:( 3041:O 3013:) 3009:( 2967:1 2964:+ 2932:= 2923:P 2909:) 2891:( 2888:O 2820:f 2790:1 2784:f 2754:= 2745:P 2730:n 2715:) 2710:) 2707:1 2704:( 2701:o 2695:1 2690:( 2660:c 2628:P 2614:c 2593:n 2580:c 2555:n 2540:) 2535:) 2532:1 2529:( 2526:o 2520:1 2515:( 2480:n 2463:n 2454:2 2443:2 2440:1 2413:n 2396:. 2394:O 2390:f 2385:S 2381:x 2377:S 2370:L 2366:O 2358:L 2338:S 2326:S 2312:0 2304:S 2300:x 2279:} 2276:1 2273:, 2270:0 2267:{ 2259:S 2255:x 2237:f 2233:f 2211:) 2208:1 2205:( 2199:+ 2194:n 2173:n 2139:3 2136:= 2133:k 2111:1 2107:T 2084:0 2080:T 2057:1 2053:S 2049:, 2043:, 2038:k 2034:S 2011:i 2007:S 1984:1 1980:T 1976:, 1971:0 1967:T 1944:k 1940:2 1936:, 1930:, 1927:8 1924:, 1921:4 1918:, 1915:2 1893:k 1889:S 1885:, 1879:, 1874:1 1870:S 1849:k 1829:2 1821:) 1818:1 1815:+ 1812:k 1809:( 1805:2 1801:= 1798:n 1778:2 1774:/ 1770:) 1767:n 1764:( 1756:2 1716:0 1710:c 1689:m 1679:c 1636:S 1610:s 1589:) 1580:s 1576:( 1573:H 1551:1 1548:+ 1544:n 1529:k 1526:1 1519:n 1514:1 1511:= 1508:k 1500:= 1497:) 1494:n 1491:( 1488:H 1464:n 1444:) 1441:n 1438:( 1435:H 1415:) 1412:n 1409:( 1406:H 1386:s 1366:) 1363:s 1360:( 1357:H 1281:n 1249:n 1227:n 1189:1 1181:s 1177:x 1170:0 1148:s 1144:x 1115:S 1107:s 1085:s 1081:w 1058:s 1054:x 1048:s 1044:w 1036:S 1028:s 997:1 991:x 988:A 967:0 964:= 959:s 956:, 953:e 949:A 926:1 923:= 918:s 915:, 912:e 908:A 885:A 850:S 842:s 820:} 817:1 814:, 811:0 808:{ 800:s 796:x 765:U 757:e 735:1 727:s 723:x 717:s 711:e 705:s 667:s 663:x 655:S 647:s 602:e 595:t 588:v 482:S 475:U 469:x 465:x 449:S 383:) 378:S 373:, 368:U 363:( 336:k 316:k 296:) 291:S 286:, 281:U 276:( 246:U 222:S 212:C 184:U 160:S 136:U 121:S 117:U 109:U 105:S 101:m 95:S 88:U 80:S 72:m 68:S 58:n

Index


combinatorics
computer science
operations research
complexity theory
set
universe
union
decision problem
optimization problem
NP-complete
Karp's 21 NP-complete problems
NP-complete
NP-hard
approximation algorithms
Covering/packing-problem pairs
Covering problems
Packing problems
Minimum set cover
Maximum set packing
Minimum edge cover
Maximum matching
Minimum vertex cover
Maximum independent set
Bin covering
Bin packing
Polygon covering
Rectangle packing
v
t

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