reverse array
public static void reverse ( int [ ] input ) { int last = input . Length - 1 ; int middle = input . Length / 2 ; for ( int i = 0 ; i <= middle ; i ++ ) { int temp = input [ i ] ; input [ i ] = input [ last - i ] ; input [ last - i ] = temp ; } } static int __gcd ( int a , int b ) { if ( b == 0 ) { return a ; } return __gcd ( b , a % b ) ; }