poj2387 Til the Cows Come Home

解题思路：最短路的模板题,注意一个细节处理即可。

见代码：

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 #define inf 0x3f3f3f3f
 const int maxn = ;
 int vis[maxn], w[maxn][maxn], d[maxn], t, n;

 void Dijkstra()
 {
     for(int i = ; i <= n; i++) d[i] = w[i][n];
     for(int i = ; i <= n; i++)
     {
         int k = -;
         int min1 = inf;
         for(int j = ; j <= n; j++)
         {
             if(vis[j]) continue;
             if(d[j] < min1)
             {
                 min1 = d[j];
                 k = j;
             }
         }
         if(k == -) break;
         vis[k] = ;
         for(int j = ; j <= n; j++)
         {

             if(vis[j]) continue;
             if(d[j] > d[k] + w[k][j] && w[k][j] < inf)
             {
                    d[j] = d[k] + w[k][j];
             }
         }
     }
     return ;
 }

 int main()
 {
     int x, y, len;
     while(~scanf("%d %d", &t, &n))
     {
         for(int i = ; i <= n; i++)
         for(int j = ; j <= n; j++)
         {
             if(i == j) w[i][j] = ;
             else w[i][j] = w[j][i] = inf;
         }
         memset(vis, , sizeof(vis));
         //for(int i = 1; i <= n; i++) d[i] = inf;
         //d[n] = 0;
         while(t-- )
         {
             scanf("%d %d %d", &x, &y, &len);
             //w[x][y] = w[y][x] = len; 刚开始没有进行if判断
             if(w[x][y] > len) w[y][x] = w[x][y] = len;
         }
         Dijkstra();
         printf("%d\n", d[]);
     }
     return ;
 }