[Solved] 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].

Question

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

Python Solution

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

        if nums[i]!=target:
            return [-1,-1]
        start=i
        
        j=l-1
        while(i<j):
            mid = i + (j-i)//2 + 1
            if nums[mid]>target:
                j = mid-1
            else:
                i = mid
        end=i
        return [start,end]
Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

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