poj1703 Find them, Catch them

思路：

关系型并查集。简化的食物链。

实现：

#include <iostream>
#include <cstdio>
using namespace std;

const int MAXN = 100000;

int a[MAXN + 10];
int par[2 * MAXN + 10];
int ran[2 * MAXN + 10];
int t, n, m, x, y;
char p;

void init(int n)
{
    for (int i = 0; i <= n; i++)
    {
        par[i] = i;
        ran[i] = 0;
    }
}

int find(int x)
{
    if (x == par[x])
        return x;
    return par[x] = find(par[x]);
}

void unite(int x, int y)
{
    x = find(x);
    y = find(y);
    if (x == y)
    {
        return;
    }
    if (ran[x] < ran[y])
    {
        par[x] = y;
    }
    else
    {
        par[y] = x;
        if (ran[x] == ran[y])
        {
            ran[x] ++;
        }
    }
}

bool same(int x, int y)
{
    return find(x) == find(y);
}

int main()
{
    cin >> t;
    while (t--)
    {
        cin >> n >> m;
        getchar();
        init(2 * n);
        for (int i = 0; i < m; i++)
        {
            scanf("%c %d %d", &p, &x, &y);
            getchar();
            x--;
            y--;
            if (p == 'D')
            {
                unite(x, y + n);
                unite(x + n, y);
            }
            else
            {
                if (same(x, y) || same(x + n, y + n))
                {
                    puts("In the same gang.");
                }
                else if (same(x + n, y) || same(x, y + n))
                {
                    puts("In different gangs.");
                }
                else
                {
                    puts("Not sure yet.");
                }
            }
        }
    }
    return 0;
}