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