Leetcode 137 Single Number II

Given an array of integers, every element appears three times except for one. Find that single one.

Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

方法一：原理同 Leetcode 136 Single Number

var singleNumber = function(nums) {
    var hash = {}
    for(var i=0; i<nums.length; i++)
        if(!hash.hasOwnProperty(nums[i]))
            hash[nums[i]] = 1
        else
            hash[nums[i]] += 1
    for(var x in hash)
        if(hash[x] < 2)
            return Number(x)
}

方法二：Bit Manipulation