Find first and last position of element in sorted array

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        def searchLeft(arr, target):
            l = 0
            r = len(arr) - 1
            while l <= r:
                mid = (l + r) // 2
                if arr[mid] < target:
                    l = mid + 1
                elif arr[mid] > target:
                    r = mid - 1
                elif arr[mid] == target:
                    r = mid - 1
            if l < 0 or l > len(arr) - 1:
                return -1
            return l if arr[l] == target else -1
        def searchRight(arr, target):
            l = 0
            r = len(arr) - 1
            while l <= r:
                mid = (l + r) // 2
                if arr[mid] < target:
                    l = mid + 1
                elif arr[mid] > target:
                    r = mid - 1
                elif arr[mid] == target:
                    l = mid + 1
            if r < 0 or r > len(arr) - 1:
                return -1
            return r if arr[r] == target else -1

        return [searchLeft(nums, target), searchRight(nums, target)]

Find First and Last Position of Element in Sorted Array

Difficulty: Medium


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

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

You must write an algorithm with O(log n) runtime complexity.

 

Example 1:

Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]

Example 2:

Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]

Example 3:

Input: nums = [], target = 0
Output: [-1,-1]

 

Constraints:

  • 0 <= nums.length <= 105
  • -109 <= nums[i] <= 109
  • nums is a non-decreasing array.
  • -109 <= target <= 109