LeetCode in Kotlin

137. Single Number II

Medium

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 1:

Input: nums = [2,2,3,2]

Output: 3

Example 2:

Input: nums = [0,1,0,1,0,1,99]

Output: 99

Constraints:

• 1 <= nums.length <= 3 * 104
• -231 <= nums[i] <= 231 - 1
• Each element in nums appears exactly three times except for one element which appears once.

Solution

class Solution {
    fun singleNumber(nums: IntArray): Int {
        var ones = 0
        var twos = 0
        for (num in nums) {
            ones = ones xor num and twos.inv()
            twos = twos xor num and ones.inv()
        }
        return ones
    }
}

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