540. Single Element in a Sorted Array.cpp

class Solution {
public:
    int singleNonDuplicate(vector<int>& nums) {
        if (nums.size() == 1)
            return nums[0];
        if (nums[0] != nums[1])
            return nums[0];
        if (nums[nums.size() - 1] != nums[nums.size() - 2])
            return nums[nums.size() - 1];
        int l = 0, h = nums.size() - 1, mid;
        while (l <= h)
        {
            mid = (l + h) / 2;
            if (nums[mid] != nums[mid + 1] && nums[mid] != nums[mid - 1])
                return nums[mid];
            else if ((nums[mid] == nums[mid + 1] && mid % 2 == 0)
                     || (nums[mid] == nums[mid - 1] && mid % 2 != 0))
                l = mid + 1;
            else
                h = mid - 1;
        }
        return -1;
    }
};