并查集

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hdu1232 畅通工程（并查集入门）

当并查集模板用

有一篇超赞的文章：http://blog.csdn.net/dellaserss/article/details/7724401

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <map>#include <algorithm>#include <cmath>#include <string>#include <queue>#include <set>#include <vector>#include <cmath>using namespace std;const int M = 1000000 * 5 + 50;int pre[1500],vis[1500];int findl(int x){    int r = x;    while(r != pre[r])r = pre[r];    int j = x;    while(pre[j] != r)    {        j = pre[j];        pre[j] = r;    }    return r;}void Max_(int a,int b){    a = findl(a);    b = findl(b);    if(a != b)    {        pre[a] = b;    }}int main(){//    freopen("in.txt","r",stdin);    int n,m;    while(~scanf("%d",&n) && n)    {        for(int i = 1; i <= n; i++)            pre[i] = i;        scanf("%d",&m);        int a,b;        for(int i = 0; i < m; i++)        {            scanf("%d%d",&a,&b);            Max_(a,b);        }        map<int,int>Map;        for(int i = 1; i <= n; i++)        {            Map[findl(i)] ++;        }        printf("%d\n",Map.size() - 1);    }    return 0;}

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