Algorithm

A straightforward approach involves using a hashmap to store the frequency of each element in the input array. After traversing the input array and storing the frequency of each element in the hashmap, we iterate through it to find the element with a frequency of 1. Return this element as it appears only once in the input array.

Step 1: Initialise an empty hashmap to store the frequency of each element.
Step 2: Populate the hashmap by iterating through the input array.
- For each element in the array, if it is already present in the hashmap, increment its frequency. Otherwise, add it to the hashmap with a frequency of 1.

Step 3: Iterate through the hashmap to find the element with a frequency of 1.
- For each key-value pair in the hashmap, if the value (frequency) is 1, return the corresponding key (element) as it appears only once in the input array.