hdu 1272 小希的迷宫

这是我第一次用并查集解决问题，其实刷这道题就是为了学习并查集，这是学长在hdu上找的模板题

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


const int N = 110000;
int par[N], mark[N];
int find1(int x)
{
    int r = x;
    while(par[r] != r) r = par[r];

    int i = x, j;
    while(i != r)
        j = par[i], par[i] = r, i = j;
    return r;
}
void unite(int x, int y)
{
    x = find1(x);
    y = find1(y);
    par[x] = y;
}
bool same(int x, int y)
{
    return find1(x) == find1(y);
}


int main()
{
    while(true)
    {
        int a, b, min1 = 0x7fffffff, max1 = 0x80000000, f = 1, flag = 1, sum = 0;
        for(int i = 0; i < N; i++)
            par[i] = i, mark[i] = 0;

        while(true)
        {
            scanf("%d%d", &a, &b); sum++;
            if(a == -1)
            {
                f = 0; break;
            }
            if(a == 0) break;

            min1 = (min1 < min(a, b)) ? min1 : min(a, b);
            max1 = (max1 > max(a, b)) ? max1 : max(a, b);
            mark[a] = mark[b] = 1;
            if(same(a, b) == true) flag = 0;
            else unite(a, b);
        }
        if(!f) break;
        if(sum == 1 && a == 0) {printf("Yes\n"); continue;}
        if(!flag) {printf("No\n"); continue;}

        int cnt = 0;
        for(int i = min1; i <= max1; i++)
            if(mark[i] && par[i] == i) cnt++;

        if(cnt == 1) printf("Yes\n");
        else printf("No\n");
    }


    return 0;
}