fig10_53.cpp

经典书籍源代码啊。。。第三版。。。数据结构与算法分析——C++描述(第3版).

/**
 * Compute all-shortest paths.
 * a contains the adjacency matrix with
 * a[ i ][ i ] presumed to be zero.
 * d contains the values of the shortest path.
 * Vertices are numbered starting at 0; all arrays
 * have equal dimension. A negative cycle exists if
 * d[ i ][ i ] is set to a negative value.
 * Actual path can be computed using path[ ][ ].
 * NOT_A_VERTEX is -1
 */
void allPairs( const matrix<int> & a,
               matrix<int> & d, matrix<int> & path ) 
{
    int n = a.numrows( );

    // Initialize d and path
    for( int i = 0; i < n; i++ )
        for( int j = 0; j < n; j++ )
        {
            d[ i ][ j ] = a[ i ][ j ];
            path[ i ][ j ] = NOT_A_VERTEX;
        }

    for( int k = 0; k < n; k++ )
        // Consider each vertex as an intermediate
        for( int i = 0; i < n; i++ )
            for( int j = 0; j < n; j++ )
                if( d[ i ][ k ] + d[ k ][ j ] < d[ i ][ j ] )
                {
                    // Update shortest path
                    d[ i ][ j ] = d[ i ][ k ] + d[ k ][ j ];
                    path[ i ][ j ] = k;
                }
}