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Difference between highest and least frequencies in an array
• Difficulty Level : Easy
• Last Updated : 12 Jul, 2019

Given an array, find the difference between highest occurrence and least occurrence of any number in an array

Examples:

```Input  : arr[] = [7, 8, 4, 5, 4, 1, 1, 7, 7, 2, 5]
Output : 2
Lowest occurring element (5) occurs once.
Highest occurring element (1 or 7) occurs 3 times

Input  : arr[] = [1, 1, 1, 3, 3, 3]
Output : 0
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

A simple solution is to use two loops to count frequency of every element and keep track of maximum and minimum frequencies.

A better solution is to sort the array in O(n log n) and check
consecutive element’s occurrence and compare their count respectively.

## C++

 `// CPP code to find the difference between highest``// and least frequencies``#include ``using` `namespace` `std;`` ` `int` `findDiff(``int` `arr[], ``int` `n)``{``    ``// sort the array``    ``sort(arr, arr + n);`` ` `    ``int` `count = 0, max_count = 0, min_count = n;``    ``for` `(``int` `i = 0; i < (n - 1); i++) {`` ` `        ``// checking consecutive elements``        ``if` `(arr[i] == arr[i + 1]) {``            ``count += 1;``            ``continue``;``        ``}``        ``else` `{``            ``max_count = max(max_count, count);``            ``min_count = min(min_count, count);``            ``count = 0;``        ``}``    ``}`` ` `    ``return` `(max_count - min_count);``}`` ` `// Driver code``int` `main()``{``    ``int` `arr[] = { 7, 8, 4, 5, 4, 1, 1, 7, 7, 2, 5 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);`` ` `    ``cout << findDiff(arr, n) << ``"\n"``;``    ``return` `0;``}`

## Java

 `// JAVA Code for Difference between``// highest and least frequencies``// in an array``import` `java.util.*;`` ` `class` `GFG {`` ` `    ``static` `int` `findDiff(``int` `arr[], ``int` `n)``    ``{``        ``// sort the array``        ``Arrays.sort(arr);`` ` `        ``int` `count = ``0``, max_count = ``0``,``            ``min_count = n;`` ` `        ``for` `(``int` `i = ``0``; i < (n - ``1``); i++) {`` ` `            ``// checking consecutive elements``            ``if` `(arr[i] == arr[i + ``1``]) {``                ``count += ``1``;``                ``continue``;``            ``}``            ``else` `{``                ``max_count = Math.max(max_count,``                                     ``count);`` ` `                ``min_count = Math.min(min_count,``                                     ``count);``                ``count = ``0``;``            ``}``        ``}`` ` `        ``return` `(max_count - min_count);``    ``}`` ` `    ``// Driver program to test above function``    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``int` `arr[] = { ``7``, ``8``, ``4``, ``5``, ``4``, ``1``,``                      ``1``, ``7``, ``7``, ``2``, ``5` `};``        ``int` `n = arr.length;`` ` `        ``System.out.println(findDiff(arr, n));``    ``}``}`` ` `// This code is contributed by Arnav Kr. Mandal.`

## Python3

 `# Python3 code to find the difference ``# between highest nd least frequencies`` ` `def` `findDiff(arr, n):``     ` `    ``# sort the array``    ``arr.sort()``     ` `    ``count ``=` `0``; max_count ``=` `0``; min_count ``=` `n``    ``for` `i ``in` `range``(``0``, (n``-``1``)):`` ` `        ``# checking consecutive elements``        ``if` `arr[i] ``=``=` `arr[i ``+` `1``]:``            ``count ``+``=` `1``            ``continue``        ``else``:``            ``max_count ``=` `max``(max_count, count)``            ``min_count ``=` `min``(min_count, count)``            ``count ``=` `0``    ``return` `max_count ``-` `min_count`` ` `# Driver Code``arr ``=` `[ ``7``, ``8``, ``4``, ``5``, ``4``, ``1``, ``1``, ``7``, ``7``, ``2``, ``5` `]``n ``=` `len``(arr)``print` `(findDiff(arr, n))`` ` `# This code is contributed by Shreyanshi Arun.`

## C#

 `// C# Code for Difference between``// highest and least frequencies``// in an array``using` `System;`` ` `class` `GFG {`` ` `    ``static` `int` `findDiff(``int``[] arr, ``int` `n)``    ``{``         ` `        ``// sort the array``        ``Array.Sort(arr);`` ` `        ``int` `count = 0, max_count = 0,``            ``min_count = n;`` ` `        ``for` `(``int` `i = 0; i < (n - 1); i++) {`` ` `            ``// checking consecutive elements``            ``if` `(arr[i] == arr[i + 1]) {``                ``count += 1;``                ``continue``;``            ``}``            ``else` `{``                ``max_count = Math.Max(max_count,``                                    ``count);`` ` `                ``min_count = Math.Min(min_count,``                                    ``count);``                ``count = 0;``            ``}``        ``}`` ` `        ``return` `(max_count - min_count);``    ``}`` ` `    ``// Driver program to test above function``    ``public` `static` `void` `Main()``    ``{`` ` `        ``int``[] arr = { 7, 8, 4, 5, 4, 1,``                       ``1, 7, 7, 2, 5 };``        ``int` `n = arr.Length;`` ` `        ``Console.WriteLine(findDiff(arr, n));``    ``}``}`` ` `// This code is contributed by vt_m.`

## PHP

 ``

Output:
``` 2
```

An efficient solution is to use hashing. We count frequencies of all elements and finally traverse the hash table to find maximum and minimum.

Below is the implementation.

## C++

 `// CPP code to find the difference between highest``// and least frequencies``#include ``using` `namespace` `std;`` ` `int` `findDiff(``int` `arr[], ``int` `n)``{``    ``// Put all elements in a hash map``    ``unordered_map<``int``, ``int``> hm;``    ``for` `(``int` `i = 0; i < n; i++)``        ``hm[arr[i]]++;`` ` `    ``// Find counts of maximum and minimum``    ``// frequent elements``    ``int` `max_count = 0, min_count = n;``    ``for` `(``auto` `x : hm) {``        ``max_count = max(max_count, x.second);``        ``min_count = min(min_count, x.second);``    ``}`` ` `    ``return` `(max_count - min_count);``}`` ` `// Driver``int` `main()``{``    ``int` `arr[] = { 7, 8, 4, 5, 4, 1, 1, 7, 7, 2, 5 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);`` ` `    ``cout << findDiff(arr, n) << ``"\n"``;``    ``return` `0;``}`

## Java

 `// Java code to find the difference between highest``// and least frequencies``import` `java.util.*;`` ` `class` `GFG``{`` ` `static` `int` `findDiff(``int` `arr[], ``int` `n)``{``    ``// Put all elements in a hash map``    ``Map mp = ``new` `HashMap<>();``    ``for` `(``int` `i = ``0` `; i < n; i++)``    ``{``        ``if``(mp.containsKey(arr[i]))``        ``{``            ``mp.put(arr[i], mp.get(arr[i])+``1``);``        ``}``        ``else``        ``{``            ``mp.put(arr[i], ``1``);``        ``}``    ``}`` ` `    ``// Find counts of maximum and minimum``    ``// frequent elements``    ``int` `max_count = ``0``, min_count = n;``    ``for` `(Map.Entry x : mp.entrySet())``    ``{``        ``max_count = Math.max(max_count, x.getValue());``        ``min_count = Math.min(min_count, x.getValue());``    ``}`` ` `    ``return` `(max_count - min_count);``}`` ` `// Driver code``public` `static` `void` `main(String[] args) ``{``    ``int` `arr[] = { ``7``, ``8``, ``4``, ``5``, ``4``, ``1``, ``1``, ``7``, ``7``, ``2``, ``5` `};``    ``int` `n = arr.length;``    ``System.out.println(findDiff(arr, n));``}``}`` ` `/* This code is contributed by PrinciRaj1992 */`

## Python3

 `# Python code to find the difference between highest ``# and least frequencies `` ` `from` `collections ``import` `defaultdict``def` `findDiff(arr,n):`` ` `    ``# Put all elements in a hash map``    ``mp ``=` `defaultdict(``lambda``:``0``)``    ``for` `i ``in` `range``(n):``        ``mp[arr[i]]``+``=``1`` ` `    ``# Find counts of maximum and minimum ``    ``# frequent elements ``    ``max_count``=``0``;min_count``=``n``    ``for` `key,values ``in` `mp.items():``        ``max_count``=` `max``(max_count,values)``        ``min_count ``=` `min``(min_count,values)`` ` `    ``return` `max_count``-``min_count`` ` ` ` `# Driver code``arr ``=` `[ ``7``, ``8``, ``4``, ``5``, ``4``, ``1``, ``1``, ``7``, ``7``, ``2``, ``5``]``n ``=` `len``(arr)``print``(findDiff(arr,n))`` ` `# This code is contributed by Shrikant13`

## C#

 `// C# code to find the difference between highest``// and least frequencies``using` `System;``using` `System.Collections.Generic;`` ` `class` `GFG``{`` ` `static` `int` `findDiff(``int` `[]arr, ``int` `n)``{``    ``// Put all elements in a hash map``    ``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);``        ``}``    ``}`` ` `    ``// Find counts of maximum and minimum``    ``// frequent elements``    ``int` `max_count = 0, min_count = n;``    ``foreach``(KeyValuePair<``int``, ``int``> entry ``in` `mp)``    ``{``        ``max_count = Math.Max(max_count, entry.Value);``        ``min_count = Math.Min(min_count, entry.Value);``    ``}`` ` `    ``return` `(max_count - min_count);``}`` ` `// Driver code``public` `static` `void` `Main(String[] args) ``{``    ``int` `[]arr = { 7, 8, 4, 5, 4, 1, 1, 7, 7, 2, 5 };``    ``int` `n = arr.Length;``    ``Console.WriteLine(findDiff(arr, n));``}``}`` ` `// This code is contributed by Princi Singh`

Output:
``` 2
```

Time Complexity : O(n)

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