Peak Index in a Mountain Array

Medium

binary-searcharray

A mountain array increases strictly to a single peak and then decreases strictly. Given a mountain array arr, return the index of the peak in O(log n).

Input: one line of space-separated integers (a valid mountain). Output: the peak index.

Example 1

Input:

0 1 0

Output:

Example 2

Input:

0 10 5 2

Output:

Example 3

Input:

3 9 8 6 4

Output:

Constraints

3 ≤ arr.length ≤ 10^5
arr is guaranteed to be a mountain.

Watch a video walkthrough

Run your code against the sample tests, or Submit to run the full suite.

Problems

Peak Index in a Mountain Array

Medium

binary-searcharray

A mountain array increases strictly to a single peak and then decreases strictly. Given a mountain array arr, return the index of the peak in O(log n).

Input: one line of space-separated integers (a valid mountain). Output: the peak index.

Example 1

Input:

0 1 0

Output:

Example 2

Input:

0 10 5 2

Output:

Example 3

Input:

3 9 8 6 4

Output:

Constraints

3 ≤ arr.length ≤ 10^5
arr is guaranteed to be a mountain.

Watch a video walkthrough

Run your code against the sample tests, or Submit to run the full suite.