Related Articles

# Find array elements with frequencies in range [l , r]

• Difficulty Level : Basic
• Last Updated : 31 May, 2021

Given an array of integers, find the elements from the array whose frequency lies in the range [l, r].

Examples:

```Input : arr[] = { 1, 2, 3, 3, 2, 2, 5 }
l = 2, r = 3
Output : 2 3 3 2 2```

Approach :

• Take a hash map, which will store the frequency of all the elements in the array.
• Now, traverse once again.
• Print the elements whose frequency lies between the range [l, r].

## C++

 `// C++ program to find the elements whose``// frequency lies in the range [l, r]``#include "iostream"``#include "unordered_map"``using` `namespace` `std;` `void` `findElements(``int` `arr[], ``int` `n, ``int` `l, ``int` `r)``{``    ``// Hash map which will store the``    ``// frequency of the elements of the array.``    ``unordered_map<``int``, ``int``> mp;` `    ``for` `(``int` `i = 0; i < n; ++i) {` `        ``// Increment the frequency``        ``// of the element by 1.``        ``mp[arr[i]]++;``    ``}` `    ``for` `(``int` `i = 0; i < n; ++i) {` `        ``// Print the element whose frequency``        ``// lies in the range [l, r]``        ``if` `(l <= mp[arr[i]] && mp[arr[i] <= r]) {``            ``cout << arr[i] << ``" "``;``        ``}``    ``}``}` `int` `main()``{``    ``int` `arr[] = { 1, 2, 3, 3, 2, 2, 5 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);``    ``int` `l = 2, r = 3;``    ``findElements(arr, n, l, r);``    ``return` `0;``}`

## Java

 `import` `java.util.HashMap;``import` `java.util.Map;` `// Java program to find the elements whose``// frequency lies in the range [l, r]``public` `class` `GFG {` `    ``static` `void` `findElements(``int` `arr[], ``int` `n, ``int` `l, ``int` `r) {``        ``// Hash map which will store the``        ``// frequency of the elements of the array.``        ``Map mp = ``new` `HashMap();` `        ``for` `(``int` `i = ``0``; i < n; ++i) {` `            ``// Increment the frequency``            ``// of the element by 1.``            ``int` `a=``0``;``            ``if``(mp.get(arr[i])==``null``){``                ``a=``1``;``            ``}``            ``else``{``                ``a = mp.get(arr[i])+``1``;``            ``}``            ``mp.put(arr[i], a);``        ``}` `        ``for` `(``int` `i = ``0``; i < n; ++i) {` `            ``// Print the element whose frequency``            ``// lies in the range [l, r]``            ``if` `(l <= mp.get(arr[i]) && (mp.get(arr[i]) <= r)) {``                ``System.out.print(arr[i] + ``" "``);``            ``}``        ``}``    ``}` `    ``public` `static` `void` `main(String[] args) {``        ``int` `arr[] = {``1``, ``2``, ``3``, ``3``, ``2``, ``2``, ``5``};``        ``int` `n = arr.length;``        ``int` `l = ``2``, r = ``3``;``        ``findElements(arr, n, l, r);` `    ``}``}``/*This code is contributed by PrinciRaj1992*/`

## Python3

 `# Python 3 program to find the elements whose``# frequency lies in the range [l, r]` `def` `findElements(arr, n, l, r):``    ` `    ``# Hash map which will store the``    ``# frequency of the elements of the array.``    ``mp ``=` `{i:``0` `for` `i ``in` `range``(``len``(arr))}` `    ``for` `i ``in` `range``(n):``        ` `        ``# Increment the frequency``        ``# of the element by 1.``        ``mp[arr[i]] ``+``=` `1` `    ``for` `i ``in` `range``(n):``        ` `        ``# Print the element whose frequency``        ``# lies in the range [l, r]``        ``if` `(l <``=` `mp[arr[i]] ``and` `mp[arr[i] <``=` `r]):``            ``print``(arr[i], end ``=` `" "``)``    ` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ``arr ``=` `[``1``, ``2``, ``3``, ``3``, ``2``, ``2``, ``5``]``    ``n ``=` `len``(arr)``    ``l ``=` `2``    ``r ``=` `3``    ``findElements(arr, n, l, r)``    ` `# This code is contributed by``# Shashank_Sharma`

## C#

 `// C# program to find the elements whose``// frequency lies in the range [l, r]``using` `System;``using` `System.Collections.Generic;` `class` `GFG``{` `    ``static` `void` `findElements(``int` `[]arr, ``int` `n, ``int` `l, ``int` `r)``    ``{``        ``// Hash map which will store the``        ``// frequency of the elements of the array.``        ``Dictionary<``int``, ``int``> mp = ``new` `Dictionary<``int``, ``int``>();` `        ``for` `(``int` `i = 0; i < n; ++i)``        ``{` `            ``// Increment the frequency``            ``// of the element by 1.``            ``int` `a = 0;``            ``if``(!mp.ContainsKey(arr[i]))``            ``{``                ``a = 1;``            ``}``            ``else``            ``{``                ``a = mp[arr[i]]+1;``            ``}``            ` `            ``if``(!mp.ContainsKey(arr[i]))``            ``{``                ``mp.Add(arr[i], a);``            ``}``            ``else``            ``{``                ``mp.Remove(arr[i]);``                ``mp.Add(arr[i], a);``            ``}``        ``}` `        ``for` `(``int` `i = 0; i < n; ++i)``        ``{` `            ``// Print the element whose frequency``            ``// lies in the range [l, r]``            ``if` `(mp.ContainsKey(arr[i]) &&``                        ``l <= mp[arr[i]] &&``                        ``(mp[arr[i]] <= r))``            ``{``                ``Console.Write(arr[i] + ``" "``);``            ``}``        ``}``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `Main(String[] args)``    ``{``        ``int` `[]arr = {1, 2, 3, 3, 2, 2, 5};``        ``int` `n = arr.Length;``        ``int` `l = 2, r = 3;``        ``findElements(arr, n, l, r);` `    ``}``}` `// This code has been contributed by 29AjayKumar`

## Javascript

 ``
Output:
`2 3 3 2 2`

Time Complexity – O(N)

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

My Personal Notes arrow_drop_up