How should I practice The Only Nonrepeating Array Element?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Mygate phone screen problems in FastPrep.

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The Only Nonrepeating Array Element

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Problem statement

Given a nonempty integer array nums, return its only value that occurs exactly once.

The input contains exactly one such value. Every other distinct value occurs at least twice, and those repeated values may have different frequencies. The array is not necessarily sorted.

Function

onlyNonrepeatingElement(nums: int[]) → int

Examples

Example 1

nums = [4,1,4,2,1]return = 2

Only 2 occurs once.

Example 2

nums = [-1,8,8,8,-1,-1,5]return = 5

The repeated values each occur three times; only 5 occurs once.

Example 3

nums = [9]return = 9

A singleton has exactly one value occurring once.

Constraints

1 <= nums.length <= 10^5
-10^9 <= nums[i] <= 10^9
Exactly one value has frequency 1; every other distinct value has frequency at least 2.