# Leetcode 137 - Single number II

Note:

• Definitely use bitwise coz it requires constant extra space.
• Because the result is a 32-bit number. Let’s just figure out every digit of it!
• From i = 0 to 31, shift every num to right and do a mask with 1, and add them all up.
• Then, we get the value of the digit based on i.
• Do a modular operation with 3 because every number except the extra repeats three times.
• The remiander is the value of current digit.
• Use << to recover it, and do a | operation with res.

Question:

Given an integer array nums where every element appears three times except for one, which appears exactly once. Find the single element and return it.

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example:

Code: