540. Single Element in a Sorted Array

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.

class Solution {
public int singleNonDuplicate(int[] nums) {
int low = 0;
int high = nums.length - 1;
int mid = 0;

while (low < high) {
mid = (low + high) / 2;
if (nums[mid] != nums[mid + 1] && nums[mid] != nums[mid - 1]) {
// 终止条件
return nums[mid];
} else if ((nums[mid] == nums[mid + 1] && mid % 2 == 0) || (nums[mid] == nums[mid - 1] && mid % 2 == 1)) {
// 算法分支
low = mid + 1;
} else {
// 算法分支
high = mid - 1;
}
}
// 终止条件
return nums[low];
}
}