46.leetcode34_search_for_a_range

1.题目描述

Given an array of integers sorted in ascending order, find the starting and ending position of a given target value.

Your algorithm's runtime complexity must be in the order of O(log n).

If the target is not found in the array, return [-1, -1].

For example,
Given [5, 7, 7, 8, 8, 10] and target value 8,
return [3, 4].

2.解题思路

双指针分别从首尾向中间移动

Python代码(47ms)

class Solution(object):
    def searchRange(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        index1=0
        index2=0
        l=len(nums)-1
        i=0
        while i<l+1:
            if nums[i]<target:
                i+=1
            else:
                index1=i
                break
        while l>=0:
            if nums[l]>target:
                l-=1
            else:
                index2=l
                break
        if target not in nums:
            return [-1,-1]
        return [index1,index2]