Compute the xor of elements from ( 1 , 1 ) to ( i , j ) and store it in prefix_xor [ i ] [ j ]
static void prefix ( int arr [ ] [ ] , int prefix_xor [ ] [ ] , int n ) { for ( int i = 1 ; i < n ; i ++ ) { for ( int j = 1 ; j < n ; j ++ ) {