Find Peak Element

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

Given an input array where num[i] ≠ num[i+1], find a peak element and return its index.

The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.

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

For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.

Solution

class Solution(object):
    def findPeakElement(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        left = 0
        right = len(nums)-1

        while left < right:
            mid = (left+right)/2
            if nums[mid] > nums[mid+1] and nums[mid] > nums[mid-1]:
                return mid

            if nums[mid] < nums[mid+1]:
                left = mid+1
            else:
                right = mid-1

        return left

public class Solution {
    public int findPeakElement(int[] nums) {
        int left = 0, right = nums.length - 1;

        while(left < right) {
            if(left + 1 == right)
                return nums[left] > nums[right] ? left : right;

            int mid = (left + right) / 2;


            if(nums[mid] > nums[mid +1] && nums[mid] > nums[mid - 1])
                return mid;

            if(nums[mid] < nums[mid+1])
                left = mid + 1;
            else
                right = mid - 1;
        }

        return left;
    }
}