Given an integer array values where every element appears exactly three times except for one element which appears exactly once, return the element that appears once. The solution must have linear runtime complexity and use only constant extra space.
Example 1
Input: [5,5,5,7,7,7,8]
Output: 8
Explanation: 8 appears once, all others appear three times.
Example 2
Input: [-10,-10,-10,0,0,0,42]
Output: 42
Explanation: 42 appears once, all others appear three times.
Example 3
Input: [100,100,100,-1,-1,-1,0]
Output: 0
Explanation: 0 appears once, all others appear three times.
Constraints
Case 1
Input: [4,4,4,9,9,9,11]
Expected: 11
Case 2
Input: [1,1,1,2,2,2,3]
Expected: 3
Case 3
Input: [-7,-7,-7,6,6,6,15]
Expected: 15
Case 4
Input: [0,0,0,-5,-5,-5,23]
Expected: 23
Case 5
Input: [8,8,8,12,12,12,-3]
Expected: -3