【HDOJ】1814 Peaceful Commission
2-SAT基础题目。
1 /* 1814 */ 2 #include <iostream> 3 #include <vector> 4 #include <algorithm> 5 #include <cstdio> 6 #include <cstring> 7 #include <cstdlib> 8 using namespace std; 9 10 #define MAXN 8005 11 12 vector<int> vc[MAXN*2]; 13 bool visit[MAXN*2]; 14 int S[MAXN*2], top; 15 int n, m; 16 17 bool dfs(int u) { 18 if (visit[u^1]) return false; 19 if (visit[u]) return true; 20 21 visit[u] = true; 22 S[top++] = u; 23 for (int i=0; i<vc[u].size(); ++i) { 24 if (!dfs(vc[u][i])) 25 return false; 26 } 27 return true; 28 } 29 30 int main() { 31 int ii, jj; 32 int i, j, k; 33 bool flag; 34 35 #ifndef ONLINE_JUDGE 36 freopen("data.in", "r", stdin); 37 #endif 38 39 while (scanf("%d %d", &n, &m) != EOF) { 40 k = n+n; 41 for (i=0; i<k; ++i) 42 vc[i].clear(); 43 memset(visit, false, sizeof(bool)*k); 44 while (m--) { 45 scanf("%d %d", &i, &j); 46 --i; 47 --j; 48 ii = (i&1) ? i-1:i+1; 49 jj = (j&1) ? j-1:j+1; 50 vc[i].push_back(jj); 51 vc[j].push_back(ii); 52 } 53 flag = true; 54 for (i=0; i<k; i+=2) { 55 if (! (visit[i]||visit[i+1])) { 56 top = 0; 57 if (!dfs(i)) { 58 while (top--) 59 visit[S[top]] = false; 60 if (!dfs(i+1)) { 61 flag = false; 62 break; 63 } 64 } 65 } 66 } 67 if (flag) { 68 for (i=0; i<k; ++i) 69 if (visit[i]) 70 printf("%d\n", i+1); 71 } else { 72 puts("NIE"); 73 } 74 } 75 76 return 0; 77 }
