// Package q852 implements a solution for https://leetcode.com/problems/peak-index-in-a-mountain-array/
package q852

func peakIndexInMountainArray(arr []int) int {
	l, r := 0, len(arr)-1
	for l < r {
		m := (l + r) / 2
		if arr[m] < arr[m+1] { // incrementing
			l = m + 1
		} else {
			r = m
		}
	}
	return l
}

var _ = peakIndexInMountainArray