Leetcode 34 - Find First and Last Position of Element in Sorted Array

Prompt: Given an sorted(ascending order) array of integers and a target value, return the starting and ending index for the area with the target value. It must be solved in O(log n).

Example:

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

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

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

Solution: We can use binary search to find the index that contains the target value. Then, we can expand left and right of that index and find the start and ending index of the target values. This solution has a runtime of O(log n) because it uses binary search.