Graph Theory: 2-Sat Template

 

1 # include <cstdio> 2 # include <vector> 3 # include <cstring> 4 using namespace STD; 5 6 const int maxn = _____; 7 8 struct twosat 9 {10 int N; 11 vector <int> G [maxn * 2]; 12 bool mark [maxn * 2]; 13 int s [maxn * 2], c; 14 15 bool DFS (int x) 16 {17 if (MARK [x ^ 1]) return false; 18 if (MARK [x]) return true; 19 mark [x] = true; 20 s [C ++] = x; 21 for (INT I = 0; I <G [X]. size (); I ++) 22 if (! DFS (G [x] [I]) return false; 23 return true; 24} 25 26 void Init (INT N) // pay attention to the number of initialization points, 27 {28 This-> N = N; 29 for (INT I = 0; I <n * 2; I ++) g [I]. clear (); 30 memset (mark, 0, sizeof (Mark); 31} 32 33 // X = xval or Y = yval34 void add_clause (int x, int xval, int y, int yval) // The number ranges from 0 ~ The n-135 {36 x = x * 2 + xval; 37 y = y * 2 + yval; 38g [x ^ 1]. push_back (y); 39G [y ^ 1]. push_back (x); 40} 41 42 bool solve () 43 {44 for (INT I = 0; I <n * 2; I ++ = 2) 45 if (! Mark [I] &! Mark [I + 1]) 46 {47 c = 0; 48 if (! DFS (I) 49 {50 while (C> 0) MARK [s [-- C] = false; 51 if (! DFS (I + 1) return false; 52} 53} 54 return true; 55} 56}; 57 58 twosat solver; 59 /////////////////////////////////////// /////////// 60 // binary search, 2-Sat usually uses 61 int L = ____, r = ____; 62 while (L <r) 63 {64 int M = L + (R-L + 1)/2; 65 if (test (M) L = m; // If M meets the condition, test returns true 66 else r = M-1; 67} 68 printf ("% d \ n ", l );

 

Graph Theory: 2-Sat Template