POJ 1251(最小生成树裸题）

POJ1251

题目：输入n表示n个点，接下来n-1行每行输入一个字母表示起点，和一个k表示有k个点与他相连，该点的名字和此边长度

求他的最小生成树

#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <iomanip>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <vector>
//const int maxn = 1e5+5;
#define ll long long
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

#define MAX INT_MAX
#define FOR(i,a,b) for( int i = a;i <= b;++i)
#define bug cout<<"--------------"<<endl
using namespace std;
int ans,n,tail;
int pre[500];
struct node
{
    int x,y,z;
}edge[5000];
bool cmp(node a,node b)
{
    return a.z<b.z;
}

int Find(int x)
{
    if(x==pre[x]) return x;
    return Find(pre[x]);
}
void clearr()
{
    memset(edge,0,sizeof(edge));
    memset(pre,0,sizeof(pre));
    ans=0;
}
int main()
{

    while(scanf("%d",&n))
    {
        if(n==0) break;
        clearr();
        FOR(i,1,n-1)
        {
            char a,b;
            int k,num;
            //scanf("%c %d",&a,&k);
            cin>>a>>k;
            FOR(j,1,k)
            {
                //scanf("%c %d",&b,&num);
                cin>>b>>num;
                edge[++tail].x=a-64;
                edge[tail].y=b-64;
                edge[tail].z=num;
            }
        }
        sort(edge+1,edge+1+tail,cmp);

        FOR(i,1,n) pre[i]=i;

        FOR(i,1,tail)
        {
            int headx=Find(edge[i].x);
            int heady=Find(edge[i].y);
            if(headx==heady) continue;
            pre[headx]=heady;
            ans+=edge[i].z;
        }
        cout<<ans<<endl;


//        FOR(i,1,tail)
//        {
//            cout<<edge[i].x<<" "<<edge[i].y<<" "<<edge[i].z<<endl;
//        }
    }
}