Make the middle row palindromic
if ( N % 2 == 1 ) { for ( i = 0 ; i < M / 2 ; i ++ ) { if ( mat [ N / 2 ] [ i ] != mat [ N / 2 ] [ M - 1 - i ] ) ans ++ ; } } if ( M % 2 == 1 ) { for ( i = 0 ; i < N / 2 ; i ++ ) {