Initializing the sum table memset ( sum , 0 , sizeof ( 0 ) ) ;
for ( int i = 0 ; i < n ; i ++ ) { int k = arr [ i ] ; for ( int j = i ; j < n ; j ++ ) { if ( i == j ) sum [ i ] [ j ] = k ; else { k += arr [ j ] ; sum [ i ] [ j ] = k ; } } }