LeetCode 137 Single Number II（只出现一次的数字 II）（*）

翻译

[code]给定一个整型数组，除了某个元素外其余的均出现了三次。找出这个元素。

备注：
你的算法应该是线性时间复杂度。你可以不用额外的空间来实现它吗？

原文

[code]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?

分析

[code]class Solution {
public:

int singleNumber(vector<int>& nums) {
    sort(nums.begin(), nums.end());
    for (int i = 1; i < nums.size() - 1; ++i) {
        if ((nums[i] != nums[i - 1]) && (nums[i] != nums[i + 1]))
            return nums[i];
    }               
    if (nums[0] != nums[1]) return nums[0];
    else if (nums[nums.size() - 1] != nums[nums.size() - 2])
        return nums[nums.size() - 1];
}
};