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?

解题思路：

int singleNumber(vector<int>& nums) {
	if (nums.size()==1) return nums[0];
	int flag=0;
	while (nums.size()>1)
	{
		 flag=0;
		int temp=nums[0];
		for(vector<int>::iterator iter=nums.begin()+1;iter!=nums.end();iter++)
		{
			if(*iter==temp)
			{
				nums.erase(iter);
				nums.erase(nums.begin());
				flag=1;
				break;
			}	
		}
		if (!flag)
		{
			return nums[0];
		}
	}
}

int singleNumber(vector<int>& nums) {
    int res=0;
    for(int i=0;i<nums.size();i++)
    res^=nums[i];
    return res;
    }