Day 13.2.txt

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.

 

Example 1:

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



class Solution {
    public int findPeakElement(int[] n) {
        if(n.length==1)
            return 0;
        else if(n.length==2)
        {
            if(n[0]>n[1])
                return 0;
            else
                return 1;
        }
        else
        {
            int i,k=n[0],k1=0;
            for(i=1;i<n.length;i++)
            {
                if(k>n[i])
                    break;
                else if(i==n.length-1)
                {
                    if(n[i]>k)
                    {
                        k=n[i];
                        k1=i;
                    }
                }
                else
                {
                    if(n[i]>n[i-1]&&n[i]>n[i+1])
                    {
                        k=n[i];
                        k1=i;
                    }
                }
            }
            return k1;
        }
    }
}