swap elements of diagonal
for ( int i = 0 ; i < N ; ++ i ) if ( i != N / 2 ) swap ( array [ i ] [ i ] , array [ i ] [ N - i - 1 ] ) ; for ( int i = 0 ; i < N ; ++ i ) { for ( int j = 0 ; j < N ; ++ j ) printf ( " ▁ % d " , array [ i ] [ j ] ) ; printf ( " STRNEWLINE " ) ; } }