POJ 1703 Find them, Catch them (并查集&利用异或的性质优化)

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http://poj.org/problem?id=1703

思路和食物链那题一样的。

完整代码：

/*297ms,1156KB*/#include<cstdio>#include<cstring>int fa[100005], rk[100005];int find(int x){if (fa[x]){int tmp = fa[x];fa[x] = find(fa[x]);/// 最终找到0这个根rk[x] ^= rk[tmp]; /// 用异或的性质优化return fa[x];}return x;}void merge(int x, int y){int xx = find(x), yy = find(y);if (xx != yy){fa[yy] = xx;rk[yy] = rk[x] ^ rk[y] ^ 1; /// 用异或的性质优化}}int main(){int t, n, m, x, y, i;char ch;scanf("%d", &t);while (t--){scanf("%d%d", &n, &m);memset(fa, 0, sizeof(fa));///以0为根memset(rk, 0, sizeof(rk));while (m--){getchar();scanf("%c%d%d", &ch, &x, &y);if (ch == 'D') merge(x, y);else{if (find(x) != find(y)) puts("Not sure yet.");else if (rk[x] == rk[y]) puts("In the same gang.");else puts("In different gangs.");}}}return 0;}

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