text: Traverse the input array and store frequencies of elements
code: Dictionary < int , int > mp = new Dictionary < int , int > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( mp . ContainsKey ( arr [ i ] ) ) { var val = mp [ arr [ i ] ] ; mp . Remove ( arr [ i ] ) ; mp . Add ( arr [ i ] , val + 1 ) ; } else { mp . Add ( arr [ i ] , 1 ) ; } }