一个失败的SPFA（A不了题Orz）

#include <stdio.h>
#include <queue>
#include <string.h>
using namespace std;
#define INF 0x3f3f3f3f
int map[108][108];
//int path[108];
int dist[108];
int vis[108];
void spfa(int n,int s)
{
    int i, v;
    queue<int>q;
    q.push(s);
    dist[s] = 0;
    vis[s] = 1;
    while(!q.empty())
    {
        v = q.front();
        q.pop();
        for(i = 1;i <= n; i++)
        {
            if(!vis[i] && map[v][i] != INF && dist[i] > dist[v] + map[v][i])
            {
                dist[i] = dist[v] + map[v][i];
                if(vis[i] == 0)
                {
                    q.push(i);
                    vis[i] = 1;
                }
            }
        }
    }
   printf("%d\n",dist[n]);
}
int main()
{
    int n, m, a, i, b, c;
    while(~scanf("%d %d",&n,&m))
    {
        memset(vis,0,sizeof(vis));
        memset(map,INF,sizeof(map));
        //memset(path,0,sizeof(path));
        memset(dist,0,sizeof(dist));
        for(i = 1;i <= n;i++)
        {
            map[i][i] = 0;
        }
      for(i = 1;i <= m;i++)
      {
          scanf("%d %d %d",&a,&b,&c);
          map[a][b] = c;
         // path[b] = a;
      }
      spfa(b,1);
    }
    return 0;
}