POJ 1611 The Suspects （并查集）

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题目链接：http://poj.org/problem?id=1611

函数：void Empty()、int Find(int x)、void Union(int r1,int r2) 这三个函数，要背熟。

# include <iostream>using namespace std;int n, m, i, j;int father[30005], num[30005];void makeSet(int n){    for(i = 0; i < n; i++)    {father[i] = i; //使用本身做根num[i] = 1;    }}int findSet(int x){    if(father[x] != x) //合并后的树的根是不变的    {            father[x] = findSet(father[x]);    }    return father[x];}void Union(int a, int b){    int x = findSet(a);    int y = findSet(b);    if(x == y)    {return;    }    if(num[x] <= num[y])    {        father[x] = y;        num[y] += num[x];    }    else    {        father[y] = x;        num[x] += num[y];    }}int main(){    while(scanf("%d %d", &n, &m)!=EOF && n != 0)    {        makeSet(n);        for(i = 0; i < m; i++)        {            int count, first, b;            scanf("%d %d",&count, &first);            for(j = 1; j < count; j++)            {                scanf("%d",&b);                Union(first,b);            }        }        printf("%d\n",num[findSet(0)]);    }    return 0;}