540. Single Element in a Sorted Array

[Tcdian]

540. Single Element in a Sorted Array

给定一个只包含整数的有序数组，每个元素都会出现两次，唯有一个数只会出现一次，找出这个数。

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

• 您的方案应该在 O(log n) 时间复杂度和 O(1) 空间复杂度中运行。

[Tcdian]

Solution

• JavaScript Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var singleNonDuplicate = function(nums) {
    let left = 0;
    let right = nums.length - 1;
    while (left <= right) {
        const mid = Math.floor((left + right) / 2);
        if (nums[mid] === nums[mid - 1]) {
            if ((right - mid) % 2 === 1) {
                left = mid + 1;
            } else {
                right = mid - 2;
            }
        } else if (nums[mid] === nums[mid + 1]) {
            if ((mid - left) % 2 === 1) {
                right = mid - 1;
            } else {
                left = mid + 2;
            }
        } else {
            return nums[mid];
        }
    }
};