https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/submissions/

first_and_last.py

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        if len(nums) == 0:
            return [-1, -1]
        if len(nums) == 1:
            if target == nums[0]:
                return [0, 0]
        def binary_search(left, right):
            mid = math.floor((left + right) / 2)
            if mid >= len(nums) or left > right:
                return -1
            num = nums[mid]
            if num == target:
                return mid
            elif target < num:
                # go left
                return binary_search(left, mid - 1)
            else:
                # go right
                return binary_search(mid + 1, right)


        a_location = binary_search(0, len(nums))
        if a_location >= 0:
            left_bound = a_location
            while left_bound >= 0 and nums[left_bound] == target: left_bound -= 1
            right_bound = a_location
            while right_bound < len(nums) and nums[right_bound] == target: right_bound += 1
            return [left_bound + 1, right_bound - 1]
        else:
            return [-1, -1]