Leetcode之Single Element in a Sorted Array

題目：

You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once. Find this single element that appears only once.

Follow up: Your solution should run in O(log n) time and O(1) space.

 

Example 1:

Input: nums = [1,1,2,3,3,4,4,8,8]
Output: 2

Example 2:

Input: nums = [3,3,7,7,10,11,11]
Output: 10

 

Constraints:

• 1 <= nums.length <= 10^5
• 0 <= nums[i] <= 10^5

代碼：

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

想法：

  二分法