First and Last Occurrences of an Element in a Sorted Array

Problem Statement

Given a sorted array and a target value, find the first and last position of the target element in the array.

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

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Examples

Input
arr = [5, 7, 7, 8, 8, 10]
target = 8

Output
[3, 4]

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Input
arr = [5, 7, 7, 8, 8, 10]
target = 6

Output
[-1, -1]

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Approach Using Binary Search

Since the array is sorted, we can use binary search to efficiently find the first and last occurrences.

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Steps to Find First Occurrence

1 Initialize left and right pointers
2 Find mid element
3 If target is found, store index and move left to find earlier