README_EN.md

540. Single Element in a Sorted Array

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Description

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

Solutions

Python3

class Solution:
    def singleNonDuplicate(self, nums: List[int]) -> int:
        left, right = 0, len(nums) - 1
        while left < right:
            mid = (left + right) >> 1
            if (mid & 1) == 1:
                mid -= 1
            if nums[mid] == nums[mid + 1]:
                left = mid + 2
            else:
                right = mid
        return nums[left]

Java

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

TypeScript

function singleNonDuplicate(nums: number[]): number {
    let left = 0, right = nums.length - 1;
    while (left < right) {
        let mid = (left + right) >> 1;
        if ((mid & 1) == 1) --mid;
        if (nums[mid] == nums[mid + 1]) {
            left = mid + 2;
        } else {
            right = mid;
        }
    }
    return nums[left];
};

Go

func singleNonDuplicate(nums []int) int {
	left, right := 0, len(nums)-1
	for left < right {
		mid := (left + right) >> 1
		if (mid & 1) == 1 {
			mid--
		}
		if nums[mid] == nums[mid+1] {
			left = mid + 2
		} else {
			right = mid
		}
	}
	return nums[left]
}

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