timus 1982 Electrification Plan(最小生成树)

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <time.h>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#define inf 10000000
#define mod 10000
typedef long long ll;
using namespace std;
const int N=6005;
const int M=50000;
int power(int a,int b,int c){int ans=1;while(b){if(b%2==1){ans=(ans*a)%c;b--;}b/=2;a=a*a%c;}return ans;}
int a[N],w[N][N],vis[N],lowcost[N];
int n,m,k;
void prim()
{
    int sum=0;lowcost[1]=-1;
    for(int i=2;i<=n;i++){
        lowcost[i]=w[1][i];
    }
    for(int i=1;i<n;i++){
        int minn=inf,k;
        for(int j=1;j<=n;j++){
            if(lowcost[j]!=-1&&lowcost[j]<minn){
                k=j;minn=lowcost[j];
            }
        }
        sum+=minn;
        lowcost[k]=-1;
        for(int j=1;j<=n;j++){
            lowcost[j]=min(lowcost[j],w[k][j]);
        }
    }
    printf("%d\n",sum);
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)scanf("%d",&a[i]);
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)scanf("%d",&w[i][j]);
    for(int i=1;i<=m;i++)for(int j=1;j<=m;j++)w[a[i]][a[j]]=0;
    prim();
    return 0;
}