Single Number

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

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int x = 0;
        for(int i = 0; i < nums.size(); i++) {
            x ^= nums[i];
        }
        return x;
    }
};