Given an unsorted array of n integers which can contains n integers. Count frequency of all elements that are present in array.

Examples:

Input : arr[] = [1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 4, 5, 5] Output : 1 -> 4 2 -> 4 3 -> 2 4 -> 1 5 -> 2

This problem can be solved in many ways, refer Count frequencies of all elements in array link. In Python, we can quickly solve this problem in using Collections module.

`# Function to count frequency of each element ` `import` `collections` ` ` `# it returns a dictionary data structure whose ` `# keys are array elements and values are their ` `# corresponding frequencies {1: 4, 2: 4, 3: 2, ` `# 5: 2, 4: 1}` `def` `CountFrequency(arr):` ` ` `return` `collections.Counter(arr) ` ` ` `# Driver function` `if` `__name__ ` `=` `=` `"__main__"` `:` ` ` ` ` `arr ` `=` `[` `1` `, ` `1` `, ` `1` `, ` `1` `, ` `2` `, ` `2` `, ` `2` `, ` `2` `, ` `3` `, ` `3` `, ` `4` `, ` `5` `, ` `5` `]` ` ` `freq ` `=` `CountFrequency(arr)` ` ` ` ` `# iterate dictionary named as freq to print` ` ` `# count of each element` ` ` `for` `(key, value) ` `in` `freq.items():` ` ` `print` `(key, ` `" -> "` `, value)` |

Output:

1 -> 4 2 -> 4 3 -> 2 4 -> 1 5 -> 2

**Related Article :**

Counting the frequencies in a list using dictionary in Python

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