least common element

How to Find Least Common Element in Unsorted Array

Given an unsorted array as an input, the goal is to find least common element or lest frequent element or least repeating element in the array. Let’s solve this problem using the following methods i.e., Method 1: Sorting and Linear Traversal and Method 2: Using Hashing.


Algorithm: Method 1- Sorting and Linear Traversal

Example 1: LeastCommonElementArray.java


Time Complexity – O(nlogn) – Since the algorithm used in Arrays.sort() offer O(nlogn) performance.

Space Complexity – O(1)

Algorithm: Method 2- Use Hashing

Using Hashing to find the least common element is the efficient solution. Below is the algorithm for the same.

Example 2: LeastCommonElementArrayHashing.java


Time Complexity – O(n)

Space Complexity – O(n)

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