LeetCode - Single Number II

Question Definition

Given an array of integers, every element appears three times except for one, which appears exactly once. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Java Solution

public int singleNumber(int[] nums) {
    int res = 0;
    for (int i = 0; i < 32; ++i) {
        int sum = 0;
        for (int j = 0; j < nums.length; ++j) {
            sum += (nums[j] >> i) & 1;
        }
        res |= (sum % 3) << i;
    }
    return res;
}