162. Find Peak Element.js

/*

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

*/

/**
 * @param {number[]} nums
 * @return {number}
 */
var findPeakElement = function(nums) {
    let n = nums.length;
    let peakElIndex;
    let min = -1/0;
    let leftEl, currEl, nextEl;
    for (let left = -1, curr = 0, next = 1; next <= n; left++, curr++, next++) {
      leftEl = left === -1 ? min : nums[left];
      currEl = nums[curr];
      nextEl = next === n ? min : nums[next];

      if (leftEl < currEl && currEl > nextEl) {
        peakElIndex = curr;
        break;
      }
    }
    return peakElIndex;
};