题目描述

blablabla

样例

class Solution(object):
    def getNumberSameAsIndex(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if not nums or len(nums) == 0:
            return -1
        left, right = 0, len(nums) - 1
        while left < right:
            mid = left + right >> 1
            if nums[mid] < mid:
                left = mid + 1
            else:
                right = mid
        if nums[right] == right:
            return nums[right]
        else:
            return -1