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