# C++ Programming Code Examples

## C++ > Data Structures and Algorithm Analysis in C++ Code Examples

### All-pairs algorithm, with a test program

``` All-pairs algorithm, with a test program #include <iostream.h> #include "matrix.h" const int NOT_A_VERTEX = -1; /** * 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 /* 1*/ for( int i = 0; i < n; i++ ) /* 2*/ for( int j = 0; j < n; j++ ) { /* 3*/ d[ i ][ j ] = a[ i ][ j ]; /* 4*/ path[ i ][ j ] = NOT_A_VERTEX; } /* 5*/ for( int k = 0; k < n; k++ ) // Consider each vertex as an intermediate /* 6*/ for( int i = 0; i < n; i++ ) /* 7*/ for( int j = 0; j < n; j++ ) /* 8*/ if( d[ i ][ k ] + d[ k ][ j ] < d[ i ][ j ] ) { // Update shortest path /* 9*/ d[ i ][ j ] = d[ i ][ k ] + d[ k ][ j ]; /*10*/ path[ i ][ j ] = k; } } /* END */ int main( ) { matrix<int> a( 4, 4 ); a[ 0 ][0 ] = 0; a[ 0 ][ 1 ] = 2; a[ 0 ][ 2 ] = -2; a[ 0 ][ 3 ] = 2; a[ 1 ][ 0 ] = 1000; a[ 1 ][ 1 ] = 0; a[ 1 ][ 2 ] = -3; a[ 1 ][ 3 ] = 1000; a[ 2 ][ 0 ] = 4; a[ 2 ][ 1 ] = 1000; a[ 2 ][ 2 ] = 0; a[ 2 ][ 3 ] = 1000; a[ 3 ][ 0 ] = 1000; a[ 3 ][ 1 ] = -2; a[ 3 ][ 2 ] = 3; a[ 3 ][ 3 ] = 0; matrix<int> d( 4, 4 ); matrix<int> path( 4, 4 ); allPairs( a, d, path ); int i; for( i = 0; i < d.numrows( ); i++ ) { for( int j = 0; j < d.numcols( ); j++ ) cout << d[ i ][ j ] << " " ; cout << endl; } for( i = 0; i < path.numrows( ); i++ ) { for( int j = 0; j < path.numcols( ); j++ ) cout << path[ i ][ j ] << " " ; cout << endl; } return 0; } ```