POJ - 1703 Find them, Catch them (种类并查集)

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int pre[300000];
int fin(int a)
{
    if (pre[a]==a) return a;
    int t=a;
    while (pre[a]!=a)
    {
        a=pre[a];
    }
    while (pre[t]!=t)
    {
        int t2=t;
        t=pre[t];
        pre[t2]=a;
    }
    return a;
}
int sam(int x, int y)
{
    return fin(x) == fin(y);
}
void join(int x, int y)
{
    int a = fin(x), b = fin(y);
    if(a != b)pre[a] = b;
}
int main()
{
    std::ios::sync_with_stdio(0);
    int n, m, i, sum = 0, a1, a2;
    scanf("%d", &sum);
    while(sum--)
    {
        scanf("%d %d", &n, &m);
        char cmd[15];
        for(i = 1; i <= 2 * n; i++)pre[i] = i;
        for(i = 1; i <= m; i++)
        {
            getchar();
            scanf("%s %d %d", &cmd, &a1, &a2);
            if(strcmp(cmd, "A") == 0)
            {
                if(sam(a1, a2 + n) || sam(a2, a1 + n))printf("In different gangs.\n");
                else if(sam(a1, a2) || sam(a1 + n, a2 + n))
                {
                    join(a1, a2);
                    join(a1 + n, a2 + n);
                    printf("In the same gang.\n");
                }
                else printf("Not sure yet.\n");
            }
            else
            {
                join(a1,a2 + n);
                join(a2, a1 + n);
            }
        }
    }
    return 0;
}