Array range queries for elements with frequency same as value | Java Program to answer Q queries to find number of times an element x appears x times in a Query subarray ; Returns the count of number x with frequency x in the subarray from start to end ; map for frequency of elements ; store frequency of each element in arr [ start ; end ] ; Count elements with same frequency as value ; Driver code ; 2D array of queries with 2 columns ; calculating number of queries
import java . util . HashMap ; import java . util . Map ; class GFG { static int solveQuery ( int start , int end , int arr [ ] ) { Map < Integer , Integer > mp = new HashMap < > ( ) ; for ( int i = start ; i <= end ; i ++ ) mp . put ( arr [ i ] , mp . get ( arr [ i ] ) == null ? 1 : mp . get ( arr [ i ] ) + 1 ) ; int count = 0 ; for ( Map . Entry < Integer , Integer > entry : mp . entrySet ( ) ) if ( entry . getKey ( ) == entry . getValue ( ) ) count ++ ; return count ; } public static void main ( String [ ] args ) { int A [ ] = { 1 , 2 , 2 , 3 , 3 , 3 } ; int n = A . length ; int [ ] [ ] queries = { { 0 , 1 } , { 1 , 1 } , { 0 , 2 } , { 1 , 3 } , { 3 , 5 } , { 0 , 5 } } ; int q = queries . length ; for ( int i = 0 ; i < q ; i ++ ) { int start = queries [ i ] [ 0 ] ; int end = queries [ i ] [ 1 ] ; System . out . println ( " Answer ▁ for ▁ Query ▁ " + ( i + 1 ) + " ▁ = ▁ " + solveQuery ( start , end , A ) ) ; } } }