540. 有序数组中的单一元素

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class Solution:
    def singleNonDuplicate(self, nums: List[int]) -> int:
        left = 0
        right = len(nums)-1
        while left<=right:
            mid = (left+right)>>1
            # if mid % 2 == 1:
            #     if mid<1 or nums[mid] != nums[mid-1]:
            #         right = mid-1
            #     else:
            #         left = mid+1
            # else:
            #     if mid+1>=len(nums) or nums[mid] != nums[mid+1]:
            #         right = mid-1
            #     else:
            #         left = mid+1
            # 以上写法太啰嗦，用异或门操作 ^ 1,可以使 偶数都+1 奇数都-1。两头的索引一定是偶数。
            if mid^1>len(nums)-1 or mid^1<0 or nums[mid] != nums[mid^1]:
                right = mid-1
            else:
                left = mid+1
        return nums[left]