find-peak-element.js

// 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.
//
// click to show spoilers.
//
// Note:
// Your solution should be in logarithmic complexity.
//
//
// Credits:Special thanks to @ts for adding this problem and creating all test cases.


/**
 * @param {number[]} nums
 * @return {number}
 */
var findPeakElement = function(nums) {
    if (nums.length === 1) return 0;
    if (nums[0] > nums[1]) return 0;
    for (var i = 1, l = nums.length - 1; i < l; i++) {
        if (nums[i] > nums[i + 1] && nums[i] > nums[i - 1]) {
            return i;
        }
    }
    if (nums[nums.length - 1] > nums[nums.length - 2]) return nums.length - 1;
};