540. Single Element in a Sorted Array

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

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

Return the single element that appears only once.

Your solution must 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 <= 105
  • 0 <= nums[i] <= 105

🧠 Thuật Toán & Kỹ Thuật

Bit Manipulation (Thao tác bit)
⏱️ Thời gian O(n)
💾 Không gian O(n)

💻 Lời Giải

Python 0540-single-element-in-a-sorted-array.py 
class Solution:
    def singleNonDuplicate(self, nums: List[int]) -> int:
        n = len(nums)
        
        if n == 1:
            return nums[0]
        if nums[n - 1] != nums[n - 2]:
            return nums[n - 1]
        
        l = 0
        r = n - 1
        ans = 0
        
        while l <= r:
            m = (l + r) >> 1
            if nums[m] == nums[m^1]:
                l = m + 1
            else:
                ans = nums[m]
                r = m - 1
        
        return ans