To store cumulative 1 's
int [ ] left = new int [ n ] ; int right [ ] = new int [ n ] ; if ( s . charAt ( 0 ) == '1' ) left [ 0 ] = 1 ; else left [ 0 ] = 0 ; if ( s . charAt ( n - 1 ) == '1' ) right [ n - 1 ] = 1 ; else right [ n - 1 ] = 0 ;