# Difference between highest and least frequencies in an array

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[0]); ` ` `  `    ``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[0]); ` ` `  `    ``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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