面试题 56 - II. 数组中数字出现的次数 II

输入：nums = [3,4,3,3]
输出：4

输入：nums = [9,1,7,9,7,9,7]
输出：1

class Solution:
    def singleNumber(self, nums: List[int]) -> int:
        bits = [0 for _ in range(32)]
        for num in nums:
            for i in range(32):
                bits[i] += (num & 1)
                num >>= 1
        res = 0
        for i in range(32):
            if bits[i] % 3 == 1:
                res += (1 << i)
        return res

class Solution {
    public int singleNumber(int[] nums) {
        int[] bits = new int[32];
        for (int num : nums) {
            for (int i = 0; i < 32; ++i) {
                bits[i] += (num & 1);
                num >>= 1;
            }
        }
        int res = 0;
        for (int i = 0; i < 32; ++i) {
            if (bits[i] % 3 == 1) {
                res += (1 << i);
            }
        }
        return res;
    }
}

/**
 * @param {number[]} nums
 * @return {number}
 */
var singleNumber = function (nums) {
  let a = 0;
  let b = 0;
  for (let num of nums) {
    a = (a ^ num) & ~b;
    b = (b ^ num) & ~a;
  }
  return a;
};