pku poj 2387 Til the Cows Come Home

最简单的最短路径
上代码……
dijkstra实现

#include < iostream >
using   namespace  std;
#define  MAX 0x7fffffff
int  map[ 1001 ][ 1001 ];
bool  s[ 1001 ];
int  d[ 1001 ];
int  n,t;
int  sum;
void  dijkstra( int  v)
{    int  a,b,c;
     int  i,j,k;
     for (i = 1 ;i <= n;i ++ )
    {    for (j = 1 ;j <= n;j ++ )
        {   map[i][j] = MAX;
        }
    }
     for (i = 1 ;i <= t;i ++ )
    {   scanf( " %d%d%d " , & a, & b, & c);
         if (c < map[a][b])
           map[a][b] = map[b][a] = c;
    }
     for (i = 1 ;i <= n;i ++ )
        d[i] = map[v][i];
    d[v] = 0 ;
    s[v] = 1 ;
     for (i = 1 ;i < n;i ++ )
    {     int  min = MAX;
          for (j = 1 ;j < n;j ++ )
         {   
              if ( ! s[j] && d[j] < min && d[j] > 0 )
             {   k = j;
                 min = d[j];
             }
         }
         s[k] = 1 ;
          for (j = 1 ;j <= n;j ++ )
         {    if ( ! s[j] && d[k] + map[k][j] < d[j] && map[k][j] < MAX)
             {   d[j] = d[k] + map[k][j];
             }
         }
    }
}
int  main()
{   
    scanf( " %d%d " , & t, & n);
    dijkstra( 1 );
    printf( " %d\n " ,d[n]);
    system( " pause " );
     return   0 ;
    
}

spfa实现

#include < iostream >
using   namespace  std;
#define  MAX 1001
#define  maxx 0x7fffffff
int  map[ 1001 ][ 1001 ];
int  n,t;
int  q[ 10 * MAX];
int  flag[MAX];
int  d[MAX];
int  spfa( int  v)
{   memset(flag, 0 , sizeof (flag)); 
     int  rear,front;
     int  now;
     int  i,j;
     for (i = 1 ;i <= n;i ++ )
       d[i] = maxx;
    d[v] = 0 ;
    rear = front = 0 ;
    q[rear ++ ] = v;
    flag[v] = 1 ;

     while (front <= rear) // 队列不为空 
    {     
          now = q[front ++ ];
          flag[now] = 0 ;
           for (i = 1 ;i <= n;i ++ )
          {   
               if (map[now][i] < maxx && map[now][i] > 0 )
              {     if (d[now] + map[now][i] < d[i])
                   {       d[i] = d[now] + map[now][i];
                            if ( ! flag[i])
                           {    flag[i] = 1 ;
                                q[rear ++ ] = i;
                           }
                   }
              }
          }
    }
     return   0 ;
}
int  main()
{    int  i,j;
     int  a,b,c;
    scanf( " %d%d " , & t, & n);
     for (i = 1 ;i <= n;i ++ )
    {    for (j = 1 ;j <= n;j ++ )
        {   map[i][j] = maxx;
        }
    }
     for (i = 1 ;i <= t;i ++ )
    {   scanf( " %d%d%d " , & a, & b, & c);
         if (c < map[a][b])
           map[a][b] = map[b][a] = c;
    }
    spfa( 1 );
    printf( " %d\n " ,d[n]);
    system( " pause " );
     return   0 ;
    
}

dijkstra用堆实现

#include < iostream >
using   namespace  std;
#define  N 1001
#define  MAX 0x7fffffff
int  h[N];
int  map[N][N];
int  d[N];
int  t,n;
int  a,b,c;
int  size;
void  minheap( int  i)
{     int  l = 2 * i;
      int  r = 2 * i + 1 ;
      int  small = i;
      if (l <= size && d[h[i]] > d[h[l]])
     {   small = l;
     }
      if (r <= size && d[h[small]] > d[h[r]])
     {  small = r;
     }
      if (small != i)
     {    int  tmp = h[i];
         h[i] = h[small];
         h[small] = tmp;
         minheap(small);
     }
}
void  build()
{    int  i;
    size = n;
     for (i = 1 ;i <= size;i ++ )
       h[i] = i;
     for (i = (size >> 1 );i >= 1 ;i -- )
    {   minheap(i);
    }
}
int  minsolve()
{   
     int  minn = h[ 1 ];
    h[ 1 ] = h[size];
    size -- ;
    minheap( 1 );
     return  minn;
}
void  de( int  i, int  key)
{   
    d[h[i]] = key;
     while (d[h[i]] < d[h[i / 2 ]] && i > 1 )
    {   
         int  tmp = h[i];
        h[i] = h[i / 2 ];
        h[i / 2 ] = tmp;
        i /= 2 ;
    }
    
}
void  solve( int  v)
{    
      int  i,j;
      for (i = 1 ;i <= n;i ++ )
     {    d[i] = MAX;
     }
     d[v] = 0 ;
     build();
      while (size >= 1 )
     {    int  u = minsolve();
          for (i = 1 ;i <= size;i ++ )
         {   if (map[u][h[i]] < MAX && d[u] + map[u][h[i]] < d[h[i]])
            {    de(i,d[u] + map[u][h[i]]);
            }  
         }
     }
}
int  main()
{   scanf( " %d%d " , & t, & n);
     int  i,j;
     for (i = 1 ;i <= n;i ++ )
    {   
         for (j = 1 ;j <= n;j ++ )
        {   
            map[i][j] = MAX;
        }
    }
     for (i = 1 ;i <= t;i ++ )
    { 
         scanf( " %d%d%d " , & a, & b, & c);
          if (c < map[a][b])
            map[a][b] = map[b][a] = c;
         
    }
    solve( 1 );
    printf( " %d\n " ,d[n]);
    system( " pause " );
     return   0 ;
}