online_judge_1012

#include <iostream>using namespace std;int Tree[1001];int findRoot(int x){    if(Tree[x] == -1)        return x;    else    {        int tmp = findRoot(Tree[x]);        Tree[x] = tmp;        return tmp;    }}int main(){    int n,m;    int a,b;    int i;    int ans;    while(cin>>n)    {        ans = 0;        if(n == 0)            break;        cin>>m;        for(i=1; i<=n; ++i)            Tree[i] = -1;        for(i=0; i<m; ++i)        {            cin>>a>>b;            a = findRoot(a);            b = findRoot(b);            if(b!=a)                Tree[a] = b;        }        for(i=1; i<=n; ++i)        {            if(Tree[i] == -1)                ans++;        }        cout<<ans-1<<endl;    }    return 0;}

这题参考着打满分帝，，并查集看似简单，但是十分好用。。前提是要掌握熟练……