畅通工程

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cstring>
#define Maxn 200
#define INF 0x3f3f3f3f
int n,m;
int lowcast[Maxn];
int nearvex[Maxn];
int edge[Maxn][Maxn];
using namespace std;

void prim(int u0)
{
    int i,j;
    int sumweight=0;
    for(i=1;i<=n;i++)
    {
        lowcast[i]=edge[u0][i];
        nearvex[i]=u0;
    }
    nearvex[u0]=-1;
    for(i=1;i<n;i++)
    {
        int mins=INF;
        int v=-1;
        for(j=1;j<=n;j++)
        {
            if(nearvex[j]!=-1 && mins>lowcast[j])
            {
                mins=lowcast[j];
                v=j;
            }
        }
        if(v!=-1)
        {
            nearvex[v]=-1;
            sumweight+=mins;
            for(j=1;j<=n;j++)
            {
                if(nearvex[j]!=-1 && lowcast[j] > edge[v][j])
                {
                    lowcast[j] = edge[v][j];
                    nearvex[j]=v;
                }
            }
        }
        else{
            printf("?\n");
            return ;
        }
    }
    printf("%d\n",sumweight);
    return ;
}
int main()
{
    while(scanf("%d%d",&m,&n)!=EOF && m!=0)
    {
        int i,j,a,b,c;
        memset(edge,0,sizeof(edge));
        for(i=0;i<m;i++){
            scanf("%d%d%d",&a,&b,&c);
            edge[a][b]=edge[b][a]=c;
        }
        for(i=1;i<=n;i++){
            for(j=1;j<=n;j++){
                if(i==j)
                    edge[i][j]=0;
                else if(edge[i][j]==0)
                    edge[i][j]=INF;
            }
        }
        prim(1);
    }
    return 0;
}