[HDU 1272] 小希的迷宫 并查集

http://acm.hdu.edu.cn/showproblem.php?pid=1272

题意：中文题辣。。。

思路：并查集，需要处理森林。。。

#include <cstdio>#include <cstring>#include <iostream>using namespace std;typedef long long ll;int pre[100005];bool vis[100005];int sta[100005], top;int Init(){    memset(vis, false, sizeof(vis));    for(int i = 0; i < 100005; i++){        pre[i] = i;    }    return 0;}int Find(int rt){    int top = 0;    while(pre[rt] != rt){        sta[top++] = rt;        rt = pre[rt];    }    while(top){        pre[sta[--top]] = rt;    }    return rt;}int Union(int x, int y){    if((x ^ y) & 1)        pre[x] = y;    else        pre[y] = x;    return 0;}int main(){    int x, y, rt;    while(~scanf("%d%d", &x, &y) && ( x != -1 || y != -1)){        Init();        rt = x;        pre[y] = rt;        bool flag = true;        vis[x] = vis[y] = true;        int maxn = x > y ? x : y;        while((x || y) && scanf("%d%d", &x, &y) && (x || y)){            if(flag){                vis[x] = vis[y] = true;                maxn = x > maxn ? x : maxn;                maxn = y > maxn ? y : maxn;                x = Find(x);                y = Find(y);            }            if(x == y)                flag = false;            if(flag){                Union(x, y);            }        }        int cnt = 0;        for(int i = 1; i <= maxn && flag; i++){            if(!vis[i])                continue;            if(pre[i] == i){                cnt++;                if(cnt >= 2){                    flag = false;                    break;                }            }        }        if(flag){            printf("Yes\n");        }        else{            printf("No\n");        }    }    return 0;}