34-find-first-and-last-position-of-element-in-sorted-array

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Description

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

Solution(Python)

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        lo = 0
        hi = len(nums)-1
        
        while lo <= hi:
            mid = (lo + hi) // 2
            if nums[lo] == nums[hi] == target:
                return [lo, hi]
            if nums[mid] < target:
                lo = mid + 1
            elif nums[mid] > target:
                hi = mid - 1
            else:
                if nums[lo] != target:
                    lo += 1
                if nums[hi] != target:
                    hi -= 1
            
        return [-1,-1]