leetcode题目：Single Number和Single Number II

题目一：

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

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

代码：

class Solution {public:    int singleNumber(int A[], int n) {        set<int>m_set;        for(int i=0;i<n;i++)        {            set<int>::iterator pos;            pos = m_set.find(A[i]);            if(pos == m_set.end())            {                m_set.insert(A[i]);            }            else            {                m_set.erase(pos);            }        }        return *(m_set.begin());    }};

题目二：

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?

class Solution {public:    int singleNumber(int A[], int n) {        map<int,int>m_map;        map<int,int>::iterator pos;        for(int i =0;i<n;i++)        {            pos = m_map.find(A[i]);            if(pos!=m_map.end())            {                m_map[A[i]]=pos->second+1;            }            else            {                m_map[A[i]]=1;            }        }        pos = m_map.begin();        while(pos->second != 1&&pos!=m_map.end())        {            pos++;        }        return pos->first;    }};