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;
}