Leetcode-34-Search for a Range-(Medium)

这道题借助二分查找算法来查找目标值的index

然后向前和向后分别搜索起始边界

注意开始排除异常值优化速度

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#!/usr/local/bin/python3 # -*- coding: utf-8 -*- __author__ = 'author'     class Solution(object):     def searchRange(self, nums, target):         """         :type nums: List[int]         :type target: int         :rtype: List[int]         """         length = len(nums)         if len(nums) == 0 or nums[0] > target or nums[length - 1] < target:             return [-1, -1]         index = self.binary_search(nums, 0, length - 1, target)         if index == -1:             return [-1, -1]         else:             start = index             end = index             for i in range(index - 1, -1, -1):                 if nums[i] == target:                     start = i                 else:                     break             for i in range(index + 1, length):                 if nums[i] == target:                     end = i                 else:                     break             return [start, end]       #二分查找算法     def binary_search(self, nums, start, end, targrt):         if start > end:             return -1         mid = start + (end - start)//2         if nums[mid] > targrt:             return self.binary_search(nums, start, mid - 1, targrt)         elif nums[mid] < targrt:             return self.binary_search(nums, mid + 1, end, targrt)         else:             return mid

另外的一种思路是寻找 target-1 和 target+1的所在位置的索引，这两个值可能不存在，那么需要相应的修改二分查找算法