text: Check if we can cut vertically at c1 , at least one apple in matrix ( r , c ) -> R - 1 , c1
code: if ( preSum [ r ] - preSum [ r ] [ c1 ] > 0 ) dp [ k ] [ r ] += dp [ k - 1 ] [ r ] [ c1 ] ; } } } } } return dp [ K ] [ 0 ] [ 0 ] ; }