描述

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]

Python

二分查找，left

class Solution:
    def searchRange(self, nums, target):
        def binarySearchLeft(A, x):
            left, right = 0, len(A) - 1
            while left <= right:
                mid = (left + right) // 2
                if x > A[mid]: left = mid + 1
                else: right = mid - 1
            return left

        def binarySearchRight(A, x):
            left, right = 0, len(A) - 1
            while left <= right:
                mid = (left + right) // 2
                if x >= A[mid]: left = mid + 1
                else: right = mid - 1
            return right

        left, right = binarySearchLeft(nums, target), binarySearchRight(nums, target)
        return (left, right) if left <= right else [-1, -1]