class Solution {
public:
int singleNumber(vector<int>& nums) {
// from discuss
int nret = 0;
for(auto val : nums)
{
nret ^= val;
}
return nret;
/* my first solution
unordered_map<int, int> map;
for(int n = 0; n < nums.size(); n++)
{
map[nums[n]] = map[nums[n]] + 1;
}
for(auto vec : nums)
{
if(map[vec] == 1)
{
return vec;
}
}
*/
}
};