Package g0801_0900.s0852_peak_index_in_a_mountain_array

Class Solution

java.lang.Object
g0801_0900.s0852_peak_index_in_a_mountain_array.Solution
public class Solution extends java.lang.Object
852 - Peak Index in a Mountain Array.

Easy

Let’s call an array arr a mountain if the following properties hold:

  • arr.length >= 3
  • There exists some i with 0 < i < arr.length - 1 such that:
    • arr[0] < arr[1] < ... arr[i-1] < arr[i]
    • arr[i] > arr[i+1] > ... > arr[arr.length - 1]

Given an integer array arr that is guaranteed to be a mountain, return any i such that arr[0] < arr[1] < ... arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1].

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 <= 104
  • 0 <= arr[i] <= 106
  • arr is guaranteed to be a mountain array.

Follow up: Finding the O(n) is straightforward, could you find an O(log(n)) solution?

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    peakIndexInMountainArray(int[] arr)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • peakIndexInMountainArray

      public int peakIndexInMountainArray(int[] arr)