并查集变型。题意就是x与y是互斥的，下列是否数据是否可保证x-y是否均为互斥。
1 #include <cstdio> 2 #include <cstring> 3 4 #define MAXN 2005 5 6 int pre[MAXN]; 7 int opp[MAXN]; 8 int n; 9 bool flag; 10 11 int find(int x) { 12 return pre[x]==x ? x:pre[x]=find(pre[x]); 13 } 14 15 void merge(int x, int y) { 16 if (!flag) return ; 17 x = find(x); 18 y = find(y); 19 if (x == y) { 20 flag = false; 21 return; 22 } 23 if (opp[x]) pre[opp[x]] = y; 24 if (opp[y]) pre[opp[y]] = x; 25 opp[x] = y; 26 opp[y] = x; 27 } 28 29 int main() { 30 int case_n, m; 31 int i, j, x, y; 32 33 scanf("%d", &case_n); 34 35 for (j=1; j<=case_n; ++j) { 36 scanf("%d %d", &n, &m); 37 for (i=1; i<=n; ++i) 38 pre[i] = i; 39 memset(opp, 0, sizeof(opp)); 40 flag = true; 41 while (m--) { 42 scanf("%d %d", &x, &y); 43 merge(x, y); 44 } 45 printf("Scenario #%d: ", j); 46 if (flag) 47 printf("No suspicious bugs found! "); 48 else 49 printf("Suspicious bugs found! "); 50 } 51 52 return 0; 53 }