HDU 1102 Constructing Roads

题目大意：已知一个连接了q条路的城镇，求最小生成树。

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

struct data{int l,x,y;}seg[10010];

int r,f[10010],n,l,cnt,x,y,fx,fy,now,p,ans;

char c;

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

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';

}

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

int main(){

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

        for(int i=0;i<=n;i++)f[i]=i;ans=p=cnt=now=0;

        for(int i=1;i<=n;i++)

        for(int j=1;j<=n;j++){

            scan(l);

            if(i<j){seg[cnt].l=l;seg[cnt].x=i;seg[cnt++].y=j;}

        }scan(r);now++;

        for(int i=0;i<r;i++){

            scan(x);scan(y);

            fx=sf(x);fy=sf(y);

            if(fx!=fy){f[fx]=fy;now++;}

        }

        sort(seg,seg+cnt,cmp);

        while(now<n){

            fx=sf(seg[p].x);fy=sf(seg[p].y);

            if(fx!=fy){f[fx]=fy;ans+=seg[p].l;now++;}

            p++;

        }

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

    }

    return 0;

}