HDU 1233 还是畅通工程

题解：最小生成树

#include <cstdio>

#include <algorithm>

using namespace std;

struct node{int a,b,l;}seg[10000];

int f[105],m,n; char c;

int sf(int x){return f[x]==x?x:f[x]=sf(f[x]);}

bool cmp(node a,node b){return a.l<b.l;}

void scan(int &x){

    while(c=getchar(),c<'0'||c>'9');x=c-'0';

    while(c=getchar(),c>='0'&&c<='9')x=x*10+c-'0';

}

int main(){

    while(~scanf("%d",&n)){

        if(n==0)break;int ans=0;

        for(int i=0;i<=n;i++)f[i]=i;

        int t=n*(n-1)/2,cnt=n-1;

        for(int i=0;i<t;i++)scan(seg[i].a),scan(seg[i].b),scan(seg[i].l);

        sort(seg,seg+t,cmp); int i=-1;

        while(cnt){

            int q=sf(seg[++i].a),w=sf(seg[i].b);

            if(q!=w)cnt--,f[q]=w,ans+=seg[i].l;

        }

        printf("%d\n",ans);

    }

    return 0;

}