D

D - Constructing Roads

思路：并查集板子

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define MAXN 110
using namespace std;
int fa[MAXN];
int n,m,tot,sum,ans;
struct nond{
    int x,y,z;
}v[20001];
int cmp(nond a,nond b){
    return a.z<b.z;
}
int find(int x){
    if(fa[x]==x)    return x;
    else  return fa[x]=find(fa[x]);
}
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++){
            int x;scanf("%d",&x);
            if(i==j)    continue;
            v[++tot].x=i;v[tot].y=j;v[tot].z=x;
        }
    scanf("%d",&m);
    for(int i=1;i<=m;i++){
        int x,y;
        scanf("%d%d",&x,&y);
        v[++tot].x=x;v[tot].y=y;v[tot].z=0;
    }
    for(int i=1;i<=n;i++)    fa[i]=i;
    sort(v+1,v+1+tot,cmp);
    for(int i=1;i<=tot;i++){
        int dx=find(v[i].x);
        int dy=find(v[i].y);
        if(dx==dy)    continue;
        fa[dy]=dx;
        sum++;ans+=v[i].z;
        if(sum==n-1)    break;
    }
    cout<<ans;
}