poj 2421 Constructing Roads

#include<iostream>            //最小生成树prim
using namespace std;
const int max_ve=105,MaxWeight=2000;
int n,edge[max_ve][max_ve],sum;        //n,m分别记录顶点数和边数
struct MinTree    //最小生成树的边
{
    int begin,end,weight;
}mintree[max_ve];
void Prim()
{
    int min,v,com,i,j,k;
    for(i=0;i<n-1;i++)    //对mintree进行初始化，顶点下标从0开始
    {
        mintree[i].begin=0;mintree[i].end=i+1;
        mintree[i].weight=edge[0][i+1];
    }
    for(i=0;i<n-1;++i)        //求n-1条边
    {
        min=MaxWeight;
        for(j=i;j<n-1;++j)
        {    
            if(mintree[j].weight<min)        //求最小权值边
            {
                min=mintree[j].weight;k=j;
            }
        }    
        swap(mintree[k],mintree[i]);    //最小边移至前端
        v=mintree[i].end;
        sum+=mintree[i].weight;
        for(j=i+1;j<n-1;++j)    //更新后面的边
        {        
            com=edge[v][mintree[j].end];
            if(com<mintree[j].weight)
            {
                mintree[j].weight=com;mintree[j].begin=v;
            }
        }
    }
}
int main()
{
    int q,a,b;
    cin>>n;
    for(int i=0;i<n;++i)
        for(int j=0;j<n;++j)
            cin>>edge[i][j];
    cin>>q;
    while(q--)
    {
        cin>>a>>b;
        edge[a-1][b-1]=edge[b-1][a-1]=0;
    }
    Prim();
    cout<<sum<<endl;
    return 0;
}