0162 - Find Peak Element

0162 - Find Peak Element

A peak element is an element that is strictly greater than its neighbors.

Given an integer array nums, find a peak element, and return its index. If the array contains multiple peaks, return the index to any of the peaks.

You may imagine that nums[-1] = nums[n] = -∞.

You must write an algorithm that runs in O(log n) time.

Examples

Input: nums = [1,2,3,1] Output: 2 Explanation: 3 is a peak element and your function should return the index number 2.

Input: nums = [1,2,1,3,5,6,4] Output: 5 Explanation: Your function can return either index number 1 where the peak element is 2, or index number 5 where the peak element is 6.

Constraints

1 <= nums.length <= 1000 -231 <= nums[i] <= 231 - 1 nums[i] != nums[i + 1] for all valid i.

Java Solution

public class Solution {
    public int findPeakElement(int[] nums) {
        int left = 0;
        int right = nums.length - 1;
        while(left < right) {
            int middle = left + (right-left) / 2;
            if(nums[middle] < nums[middle+1]) left = middle+1;
            else if (nums[middle] > nums[middle+1]) right = middle;
        }
        return left;
    }
}