0852: Peak Index in a Mountain Array

Problem Statement

You are given an integer mountain array arr of length n where the values increase to a peak element and then decrease.

Return the index of the peak element.

Your task is to solve it in O(log(n)) time complexity.

Example 1:

Input: arr = [0,1,0]

Output: 1

Example 2:

Input: arr = [0,2,1,0]

Output: 1

Example 3:

Input: arr = [0,10,5,2]

Output: 1

Constraints:

  • 3 <= arr.length <= 105
  • 0 <= arr[i] <= 106
  • arr is guaranteed to be a mountain array.

Code Solution