Problem Statement

Given an array of integers nums where each element appears three times, and one element appears exactly once, return the single element.

Note: You must solve the problem with linear runtime complexity and use only constant extra space.

Examples

• Example 1:
  • Input: nums = [4, 3, 3, 3]
  • Expected Output: 4
  • Justification: 4 is the only number that appears once, while 3 appears three times.
• Example 2:
  • Input: nums = [99, 1, 99, 99, 2, 2, 2]
  • Expected Output: 1
  • Justification: 1 appears exactly once whereas 99 and 2 each appear three times.
• Example 3:
  • Input: nums = [0, 7, 2, 7, 2, 7, -1, 2, -1, -1]
  • Expected Output: 0
  • Justification: 0 is the unique number appearing once, while 7, 2 and -1 appear three times.

Try it yourself

Try solving this question here: