Hust 1017 exact cover DLX

A matrix of n × m rows. Each grid may be 0 or 1. Now let you select several columns so that each column has only one 1. (precise coverage of template questions)

Solution:

Dancing links Template

About the dancing links presented several must-see: http://par.buaa.edu.cn/acm-icpc/filepool/r/35/

The kuangbin board used by the Board (or suitable for cattle ..)

Solution:

1 // file name: hust1017.cpp 2 // Author: darkdream 3 // created time: saturday, October 04, 2014, 57 seconds, 4 5 # include <vector> 6 # include <list> 7 # include <map> 8 # include <set> 9 # include <deque> 10 # include <stack> 11 # include <bitset> 12 # include <algorithm> 13 # include <functional> 14 # include <numeric> 15 # include <utility> 16 # include <sstream> 17 # include <iostream> 18 # include <iomanip> 19 # include <cstdio> 20 # Include <cmath> 21 # include <cstdlib> 22 # include <cstring> 23 # include <ctime> 24 # define ll long 25 const int maxnode = 100010; 26 const int maxm = 1010; 27 const int maxn = 1010; 28 using namespace STD; 29 struct DLX 30 {31 int n, m, size; 32 int L [maxnode], R [maxnode], U [maxnode], d [maxnode], row [maxnode], Col [maxnode]; 33 int anSd, ANS [maxn]; 34 int H [maxn], s [maxm]; 35 void Init (INT _ n, int _ m) 36 {37 n = _ n; 38 m = _ m; 39 for (INT I = 0; I <= m; I ++) 40 {41 s [I] = 0; // s represents the color of each column 42 U [I] = d [I] = I; 43 L [I] = I-1; 44 R [I] = I + 1; 45} 46 R [m] = 0; L [0] = m; 47 size = m; 48 for (INT I = 1; I <= N; I ++) 49 H [I] =-1; // H [I] indicates the header 50} 51 void Link (INT R, int c) 52 {53 + + s [col [++ size] = C]; 54 row [size] = r; 55 d [size] = d [c]; 56 U [d [c] = size; 57 U [size] = C; 58 D [c] = size; 59 If (H [R] <0) H [R] = L [size] = R [size] = size; 60 else 61 {62 R [size] = R [H [R]; 63 l [R [H [R] = size; 64 L [size] = H [R]; 65 R [H [R] = size; // insert to the right of H [R] 66} 67} 68 void remove (INT c) // column as the unit, horizontal 69 {70 L [R [c] = L [c]; R [L [c] = R [c]; 71 for (INT I = d [c]; I! = C; I = d [I]) 72 for (Int J = R [I]; J! = I; j = R [J]) 73 {74 U [d [J] = U [J]; 75 d [U [J] = d [J]; 76 -- s [col [J]; 77} // delete a column, row K 78} 79 void resume (int c) 80 {81 L [R [c] = R [L [c] = C; 82 For (INT I = U [c]; I! = C; I = U [I]) 83 for (Int J = L [I]; J! = I; j = L [J]) 84 {85 U [d [J] = J; 86 d [U [J] = J; 87 + + s [col [J]; 88} 89} 90 bool Dance (INT d) 91 {92 If (R [0] = 0) 93 {94 anSd = D; // The Answer length is 95 return true; 96} 97 int c = R [0]; 98 for (INT I = R [c]; I! = 0; I = R [I]) 99 If (s [I] <s [c]) 100 c = I; 101 remove (C ); 102 for (INT I = d [c]; I! = C; I = d [I]) 103 {104 ans [d] = row [I]; 105 for (Int J = R [I]; J! = I; j = R [J]) Remove (COL [J]); 106 If (Dance (D + 1) return true; 107 for (Int J = L [I]; J! = I; j = L [J]) Resume (COL [J]); 108} 109 resume (c); 110 return false; 111} 112}; 113 114 DLX g; 115 int main () {116 int n, m; 117 while (scanf ("% d", & N, & M )! = EOF) 118 {119G. init (n, m); 120 int num, J; 121 for (INT I = 1; I <= N; I ++) 122 {123 scanf ("% d ", & num); 124 while (Num --) 125 {126 scanf ("% d", & J); 127G. link (I, j); 128} 129} 130 If (! G. dance (0) printf ("NO \ n"); 131 else {132 printf ("% d", G. anSd); 133 for (INT I = 0; I <G. anSd; I ++) 134 printf ("% d", G. ans [I]); 135 printf ("\ n"); 136} 137 138 return 0; 139}

View code

 

Hust 1017 exact cover DLX