学步园

//注意陷阱，还有，尽量不要用memset初始化二维数组

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
#define INFINITY 100000000
const int maxn = 210;

int N,M;
int S,T;

int G[maxn][maxn];
int Dist[maxn];
bool final[maxn];

void Dijkstra(int v0)
{
     
     int min;
     int k;
     for(int v = 0; v < N; v++)
     {
             final[v] = false;
             Dist[v] = G[v0][v];
     }
     
     Dist[v0] = 0;
     final[v0] = true;
     for(int v = 1; v < N; v++)
     {
             min = INFINITY;
             for(int w = 0; w < N; w++)
             {
                     if((!final[w]) && Dist[w] < min)
                     {
                            min = Dist[w];
                            k = w;
                     }
             }             
             
             final[k] = 1;
             for(int w = 0; w < N; w++)
             {
                     if((!final[w]) && Dist[k] + G[k][w] < Dist[w])
                     {
                           Dist[w] = Dist[k] + G[k][w];
                     }
             }
     }
}


int main()
{
    while(cin>>N>>M)
    {
          int x,y,d;
          for(int i = 0; i < N; i++)
          {
                  G[i][i] = 0;
                  for(int j = 0; j < N ;j ++)
                  {
                          G[i][j] = INFINITY;
                  }
          }
          //for(int i = 0; i < N; i++)
                  
          for(int i = 0; i < M; i++)
          {
                  cin>>x>>y>>d;
                  if(d < G[x][y])
                  {
                   G[x][y] = d;
                   G[y][x] = d;
                  }
          }
          cin>>S>>T;
          memset(Dist,INFINITY,sizeof(Dist));
          Dijkstra(S);
          if(final[T])
                 cout<<Dist[T]<<endl; 
          else
                 cout<<"-1"<<endl;
    }
    return 0;
}