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# Numbers with prime frequencies greater than or equal to k

• Difficulty Level : Medium
• Last Updated : 24 May, 2021

Given an array, find elements that appear a prime number of times in the array with a minimum k frequency (frequency >= k).

Examples :

```Input : int[] arr = { 11, 11, 11, 23, 11, 37, 51,
37, 37, 51, 51, 51, 51 };
k = 2
Output : 37, 51
Explanation :
11's count is 4, 23 count 1, 37 count 3, 51 count 5.
37 and 51 are two number that appear prime number of
time and frequencies greater than or equal to k.

Input : int[] arr = { 11, 22, 33 } min Occurrence = 1
Output : -1
None of the count is prime number of times ```

Approach :
1. Create a Map that holds the number as Key and value as its occurrences in the input array.
2. Iterate the Map keys and look for the values corresponding to their keys, return the key which
has minimum value fulfilling condition key’s value is a prime number and >= min occurrence provided
as input.

## C++

 `// C++ code to find number``// occurring prime number``// of times with frequency >= k``#include ``using` `namespace` `std;` `// Check if the number of``// occurrences are primes``// or not``bool` `isPrime(``int` `n)``{``    ``// Corner case``    ``if` `(n <= 1) ``return` `false``;` `    ``// Check from 2 to n-1``    ``for` `(``int` `i = 2; i < n; i++)``        ``if` `(n % i == 0)``            ``return` `false``;` `    ``return` `true``;``}` `// Function to find number``// with prime occurrences``void` `primeOccurences(``int` `arr[], ``int` `k)``{``    ``unordered_map<``int``, ``int``> map;``    ` `    ``// Insert values and``    ``// their frequencies``    ``for` `(``int` `i = 0; i < 12; i++)``        ``map[arr[i]]++;` `    ``// Traverse map and find``    ``// elements with prime``    ``// frequencies and frequency``    ``// at least k``    ``for` `(``auto` `x : map)``    ``{``        ``if` `(isPrime(x.second) &&``                    ``x.second >= k)``            ``cout << x.first << endl;``    ``}``}` `// Driver code``int` `main()``{``    ``int` `arr[] = {11, 11, 11, 23,``                 ``11, 37, 37, 51,``                 ``51, 51, 51, 51};``    ``int` `k = 2;` `    ``primeOccurences(arr, k);``    ``return` `0;``}` `// This code is contributed by``// Manish Shaw(manishshaw1)`

## Java

 `// Java code to find number occurring prime``// number of times with frequency >= k``import` `java.util.*;` `public` `class` `PrimeNumber {` `    ``// Function to find number with prime occurrences``    ``static` `void` `primeOccurences(``int``[] arr, ``int` `k)``    ``{``        ``Map map = ``new` `HashMap<>();` `        ``// Insert values and their frequencies``        ``for` `(``int` `i = ``0``; i < arr.length; i++) {``            ``int` `val = arr[i];` `            ``int` `freq;``            ``if` `(map.containsKey(val)) {``                ``freq = map.get(val);``                ``freq++;``            ``}``            ``else``                ``freq = ``1``;``            ``map.put(val, freq);``        ``}` `        ``// Traverse map and find elements with``        ``// prime frequencies and frequency at``        ``// least k``        ``for` `(Map.Entry entry :``                               ``map.entrySet()) {``            ``int` `value = entry.getValue();``            ``if` `(isPrime(value) && value >= k)``                ``System.out.println(entry.getKey());``        ``}``    ``}` `    ``// Check if the number of occurrences``    ``// are primes or not``    ``private` `static` `boolean` `isPrime(``int` `n)``    ``{` `        ``if` `((n > ``2` `&& n % ``2` `== ``0``) || n == ``1``)``            ``return` `false``;       ` `        ``for` `(``int` `i = ``3``; i <= (``int``)Math.sqrt(n);``             ``i += ``2``) {``            ``if` `(n % i == ``0``)``                ``return` `false``;           ``        ``}``        ``return` `true``;``    ``}` `    ``// Driver code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int``[] arr = { ``11``, ``11``, ``11``, ``23``, ``11``, ``37``,``                      ``37``, ``51``, ``51``, ``51``, ``51``, ``51` `};``        ``int` `k = ``2``;` `        ``primeOccurences(arr, k);``    ``}``}`

## Python3

 `# Python3 code to find number``# occurring prime number of``# times with frequency >= k` `# Function to find number``# with prime occurrences``def` `primeOccurences(arr, k):``    ``map` `=` `{}` `    ``# Insert values and their frequencies``    ``for` `val ``in` `arr:``        ``freq ``=` `0``        ` `        ``if` `val ``in` `map` `:``            ``freq ``=` `map``[val]``            ``freq ``+``=` `1``            ` `        ``else` `:``            ``freq ``=` `1``        ``map``[val] ``=` `freq` `    ``# Traverse map and find elements``    ``# with prime frequencies and``    ``# frequency at least k``    ``for` `entry ``in` `map` `:``        ``value ``=` `map``[entry]``        ` `        ``if` `isPrime(value) ``and` `value >``=` `k:``            ``print``(entry)` `# Check if the number of occurrences``# are primes or not``def` `isPrime(n):` `    ``if` `(n > ``2` `and` `not` `n ``%` `2``) ``or` `n ``=``=` `1``:``        ``return` `False`     `    ``for` `i ``in` `range``(``3``, ``int``(n``*``*``0.5` `+` `1``), ``2``):``        ``if` `not` `n ``%` `i:``            ``return` `False``            ` `    ``return` `True`  `# Driver code` `arr ``=` `[ ``11``, ``11``, ``11``, ``23``, ``11``, ``37``,``        ``37``, ``51``, ``51``, ``51``, ``51``, ``51` `]``k ``=` `2` `primeOccurences(arr, k)`  `# This code is contributed by Ansu Kumari.`

## C#

 `// C# code to find number``// occurring prime number``// of times with frequency >= k``using` `System;``using` `System.Collections.Generic;` `class` `GFG``{` `    ``// Function to find number``    ``// with prime occurrences``    ``static` `void` `primeOccurences(``int``[] arr,``                                ``int` `k)``    ``{``        ``Dictionary<``int``, ``int``> map =``                   ``new` `Dictionary<``int``, ``int``>();``        ` `        ``// Insert values and``        ``// their frequencies``        ``for` `(``int` `i = 0; i < arr.Length; i++)``        ``{``            ``int` `val = arr[i];` `            ``int` `freq;``            ``if` `(map.ContainsKey(val))``            ``{``                ``freq = map[val];``                ``freq++;``                ``map.Remove(val);``            ``}``            ``else``                ``freq = 1;``            ``map.Add(val, freq);``        ``}` `        ``// Traverse map and find elements``        ``// with prime frequencies and``        ``// frequency atleast k``        ``foreach` `(KeyValuePair<``int``, ``int``>``                           ``pair ``in` `map)``        ``{``            ``int` `value = pair.Value;``            ``if` `(isPrime(value) &&``                        ``value >= k)``                ``Console.WriteLine(pair.Key);``        ``}``    ``}` `    ``// Check if the number``    ``// of occurrences``    ``// are primes or not``    ``static` `bool` `isPrime(``int` `n)``    ``{``        ``if` `((n > 2 &&``             ``n % 2 == 0) || n == 1)``            ``return` `false``;    ` `        ``for` `(``int` `i = 3;``                 ``i <= (``int``)Math.Sqrt(n);``                 ``i += 2)``            ``{``                ``if` `(n % i == 0)``                    ``return` `false``;        ``            ``}``        ``return` `true``;``    ``}` `    ``// Driver code``    ``static` `void` `Main()``    ``{``        ``int``[] arr = ``new` `int``[]{11, 11, 11, 23, 11, 37,``                              ``37, 51, 51, 51, 51, 51};``        ``int` `k = 2;` `        ``primeOccurences(arr, k);``    ``}``}` `// This code is contributed by``// Manish Shaw(manishshaw1)`

## Javascript

 ``
Output :
```37
51```

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