Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element that appears only once.
Example 1:
Input: [1,1,2,3,3,4,4,8,8] Output: 2
Example 2:
Input: [3,3,7,7,10,11,11] Output: 10
Note: Your solution should run in O(log n) time and O(1) space.
思路:
二分查找。
class Solution { public: int singleNonDuplicate(vector<int>& nums) { int n = nums.size(), left = 0, right = n - 1; while (left < right) { int mid = left + (right - left) / 2; if (mid % 2 == 0) { if (nums[mid] == nums[mid - 1])right = mid - 2; else if (nums[mid] == nums[mid + 1])left = mid + 2; else return nums[mid]; } else { if (nums[mid] == nums[mid - 1])left = mid + 1; else if (nums[mid] == nums[mid + 1])right = mid - 1; } } return nums[left]; } };