Find Peak Element
01 · Problem
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.
02 · Examples
nums = [1,2,3,1]
2
3 is a peak element at index 2.
nums = [1,2,1,3,5,6,4]
5
6 is a peak element at index 5. Index 1 (value 2) is also a valid answer.
nums = [1]
0
Since nums[-1] and nums[1] are both -∞, nums[0] = 1 is a peak.
03 · Constraints
- 011 <= nums.length <= 1000
- 02-231 <= nums[i] <= 231 - 1
- 03nums[i] != nums[i + 1] for all valid i.
04 · Optimal complexity
- Time
- O(log n)
- Space
- O(1)
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