poj 1251（kruskal算法，并查集）

#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
int ancestor[900];
struct Node{
    int x,y,value;
}node[900];
bool cmp(Node n1,Node n2){
    return n1.value<n2.value;
}
int Find(int x){
    if(ancestor[x]!=x)
        ancestor[x] = Find(ancestor[x]);
    return ancestor[x];
}
void Union(int x,int y){
    int px = Find(x);
    int py = Find(y);
    Find(2); 
    ancestor[px] = py;
    Find(2);
}
bool IsSame(int x,int y){
    return Find(x)==Find(y);
} 
int main(){
    int i,j,n,cp,value,count,ans,ans_count;
    char c,next;
    while(scanf("%d",&n)==1&&n){
        count = 0;
        for(i=0;i<n-1;i++){
            cin>>c>>cp;
            for(j=0;j<cp;j++){
                cin>>next>>value;
                if(i<next-'A'){
                    node[count].x = i;
                    node[count].y = next-'A';
                }
                else{
                    node[count].x = next-'A';
                    node[count].y = i;
                }
                node[count].value = value;
                count++;
            }
        }
        sort(node,node+count,cmp);
//        for(i=0;i<count;i++){
//            cout<<i<<" "<<node[i].x<<" "<<node[i].y<<" "<<node[i].value<<endl;
//        }
        for(i=0;i<n;i++){
            ancestor[i] = i;
        }
        ans = 0;
        ans_count = 0;
        for(i=0;i<count;i++){
            if(!IsSame(node[i].x,node[i].y)){
                Union(node[i].x,node[i].y);
                ans += node[i].value;
                ans_count++;
                if(ans_count==n-1){
                    break;
                }
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}