Listing 1: The program resulting from next_permutation
#include <iostream> #include <algorithm> int main() { int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; int count = 0; do { if ( ( a[0] + a[1] + a[2] ) == 17 && ( a[0] + a[3] + a[6] ) == 17 && ( a[2] + a[5] + a[8] ) == 17 && ( a[2] + a[4] + a[6] ) == 17 && ( a[6] + a[7] + a[8] ) == 17 ) { std::cout << count << " : "; for ( int i = 0 ; i < 9 ; i++ ) std::cout << a[ i ] << " "; std::cout << "\n"; } count++; } while ( std::next_permutation( a, a + 9 ) ); std::cout << count << " permutations were tested\n"; return 0; } End of Listing