Store frequencies of array elements
HashMap < Integer , Integer > frequency = new HashMap < Integer , Integer > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( frequency . containsKey ( arr [ i ] ) ) { frequency . put ( arr [ i ] , frequency . get ( arr [ i ] ) + 1 ) ; } else { frequency . put ( arr [ i ] , 1 ) ; } } int count = 0 ;