LeetCode: Find Peak Element Solution

Approach

Start with the mid of range [left, right]

Compare nums[mid] with two adjacent elements

• if fits, mid is the result
• if not fit, shorten the range

Implementation

1/**
2 * @param {number[]} nums
3 * @return {number}
4 */
5var findPeakElement = function (nums) {
6  const recursion = (left, right) => {
7    const mid = Math.floor((left + right) / 2)
8    if (nums[mid] < nums[mid - 1]) {
9      return recursion(left, mid - 1)
10    } else if (nums[mid] < nums[mid + 1]) {
11      return recursion(mid + 1, right)
12    } else {
13      return mid
14    }
15  }
16
17  return recursion(0, nums.length - 1)
18}

References

Algorithmic Thinking, Peak Finding (MIT 6.006 Introduction to Algorithms, Fall 2011, Part 1)