G - 小希的迷宫（并查集）

#include <cstdio>
#include <algorithm>
using namespace std;
int arr[100010],  mark[100010], flag;
int findx(int x)
{
    int r = x;
    while(arr[r] != r)
        r = arr[r];
    return r;
}
void fix(int a, int b)
{
    int fx = findx(a);
    int fy = findx(b);
    if(fx != fy)
        arr[fx] = fy;
    else
        flag = 0;
}
int main()
{
    int a, b, cnt;
    while(scanf("%d%d", &a, &b) && (a != -1 && b != -1))
    {
        flag = 1, cnt = 0;
        if(a == 0 && b == 0)
        {
            printf("Yes\n");
            continue;
        }
        for(int i = 0; i < 100010; i++)
        {
            arr[i] = i;
            mark[i] = 0;
        }

        //int mi = 100010, ma = -1;
        while(a || b)
        {
            /* if(ma < max(a, b))
                ma = max(a, b);
             if(mi > min(a, b));
                mi = min(a, b);*/
            fix(a, b);
            mark[a] = mark[b] = 1;
            scanf("%d%d", &a, &b);
        }
        for(int i = 1; i <= 100000; i++)
        {
            if(arr[i] == i && mark[i])
                cnt++;
            if(cnt > 1)
            {
                flag = 0;
                break;
            }
        }
        if(flag == 1)
            printf("Yes\n");
        else
            printf("No\n");

    }
    return 0;
}