Create map for each element
Map map = new HashMap ( ) ; for ( int i = 0 ; i < MAXN ; ++ i ) map . put ( i , 0 ) ; for ( int i = 0 ; i < n ; ++ i ) map . put ( arr [ i ] , 1 ) ; int sum = 0 ; for ( int i = 0 ; i < n ; ++ i ) { int num = arr [ i ] ;