并查集 示例 ： poj 1703 [Find them, Catch them 帮派之争]

#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <vector>
#include <stack>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <map>
#include <set>
#include <iterator>
#include <algorithm>
#include <functional>
#include <utility>
#include <sstream>
#include <climits>
#include <cassert>
#define MID(x,y) ( ( x + y ) >> 1 )
#define L(x) ( x << 1 )
#define R(x) ( x << 1 | 1 )
#define BUG puts("here!!!");
#define STOP system("pause");

using namespace std;
const int N = 100005;
int f[N+N];
int n, m;
int find(int x) {
	if(f[x] < 0) return x;
	return f[x] = find(f[x]);
}
int main() {
	int loop;
	cin >> loop;
	while(loop--) {
		scanf("%d%d", &n, &m);
		memset(f, 255, sizeof(f));
		while(m--) {
			int a, b;
			char s[3];
			scanf("%s%d%d", s, &a, &b);
			if(s[0] == 'A') {
				if(find(a) != find(b) && find(a) != find(b+n)) {
					printf("Not sure yet.\n");
				}
				else if(find(a) == find(b)) {
					printf("In the same gang.\n");
				}
				else printf("In different gangs.\n");
			}
			else {
				if(find(a) != find(b+n)) {
					f[find(a)] = find(b+n);
					f[find(b)] = find(a+n);
				}
			}
		}
	}
	return 0;
}

Sample Input
1
5 5
A 1 2
D 1 2
A 1 2
D 2 4
A 1 4
Sample Output
Not sure yet.
In different gangs.
In the same gang.