历届试题 城市建设

错误代码：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <cstring>
#include <climits>
#include <cmath>
#include <cctype>

const int inf = 0x7f7f7f7f;//2139062143
typedef long long ll;
using namespace std;

int map1[10010][10010];
int visit[10010];
int lowdist[10010];
int n;

void Prim()
{
    int sum = 0;
    memset(visit,0,sizeof(visit));
    for(int i=0; i<=n; i++)
    {
        lowdist[i] = map1[1][i];
    }
    int k;
    visit[1] = 0;
    for(int i=1; i<=n; i++)
    {
        int min2 = inf;
        for(int j=0; j<=n; j++)
        {
            if(!visit[i] && lowdist[i] < min2)
            {
                min2 = lowdist[i];
                k = i;
            }
        }
        visit[k] = 1;
        sum += lowdist[k];
        for(int j=0; j<=n; j++)
        {
            if(!visit[j] && map1[k][j] < lowdist[j])
            {
                lowdist[j] = map1[k][j];
            }
        }
    }
    printf("%d\n",sum);
}

int main()
{
    int m;
    while(scanf("%d%d",&n,&m) != EOF)
    {
        memset(map1,inf,sizeof(map1));
        int a,b,c;
        for(int i=0; i<m; i++)
        {
            scanf("%d%d%d",&a,&b,&c);
            map1[a][b] = map1[b][a] = c;
        }
        for(int i=1; i<=n; i++)
        {
            scanf("%d",&a);
            if(a != -1)
                map1[i][0] = map1[0][i] = a;
            else
                map1[i][0] = map1[0][i] = inf;
        }
        Prim();
    }
    return 0;
}