text: Finding prefix sum
code: for ( int s = min_x ; s <= max_x ; s ++ ) { if ( weight_at_x . get ( s ) == null ) sum_till . add ( sum_till . lastElement ( ) ) ; else sum_till . add ( sum_till . lastElement ( ) + weight_at_x . get ( s ) ) ; } int total_sum = sum_till . lastElement ( ) ; int partition_possible = 0 ; for ( int i = 1 ; i < sum_till . size ( ) ; i ++ ) { if ( sum_till . get ( i ) == total_sum - sum_till . get ( i ) ) partition_possible = 1 ;