7 - Medium - 搜索范围

给定一个按照升序排列的整数数组 nums，和一个目标值 target。找出给定目标值在数组中的开始位置和结束位置。

你的算法时间复杂度必须是 O(log n) 级别。

如果数组中不存在目标值，返回 [-1, -1]。

示例 1:

输入: nums = [5,7,7,8,8,10], target = 8
输出: [3,4]
示例 2:

输入: nums = [5,7,7,8,8,10], target = 6
输出: [-1,-1]

左右夹逼

class Solution:
    def searchRange(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        if not nums:
            return [-1, -1]
        left, right = 0, len(nums) - 1
        while nums[left] != target or nums[right] != target:
            no_change = True
            if nums[left] != target:
                no_change = False
                left += 1
            if nums[right] != target:
                right -= 1
                no_change = False
            if no_change or left >= right:
                break
        if left < len(nums) and nums[left] == target:
            return [left, right]
        else:
            return [-1, -1]

36ms，二分查找

class Solution:
    def searchRange(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        start = self.firstGreaterEqaul(nums, target)
        if start==len(nums) or nums[start]!=target:
            return [-1, -1]
        return [start, self.firstGreaterEqaul(nums, target+1)-1]
    def firstGreaterEqaul(self, nums, target):
        lo, hi = 0, len(nums)
        while lo<hi:
            mid = (hi+lo)//2
            if nums[mid]<target:
                lo = mid + 1
            else:
                hi = mid
        return lo