Find Peak Element - LeetCode : Swift

Find Peak Element - LeetCode

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

Given a 0-indexed 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] = -∞. In other words, an element is always considered to be strictly greater than a neighbor that is outside the array.

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] <= 2^231 - 1
• nums[i] != nums[i + 1] for all valid i.

Solution

class Solution {
    func findPeakElement(_ nums: [Int]) -> Int {
        
        if nums.count == 1 {
            return 0
        } else if nums[0] > nums[1] {
            return 0
        } else if nums[nums.count - 1] > nums[nums.count - 2]{
            return nums.count - 1
        }
        for index in 1..<(nums.count - 1) {
            if nums[index] > nums[index + 1] && nums[index] > nums[index - 1] {
                return index
            }
        }
        return -1
    }
}