Find Peak Element
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 2.
Example 2:
Input: nums = [1,2,1,3,5,6,4]
Output: 5
Explanation: Your function can return either index 1 (where the peak element is 2) or index 5 (where the peak element is 6).
Examples
Example 1
Input: nums = [1,2,3,1]
Output: 2
Explanation: 3 is a peak element at index 2.
Example 2
Input: nums = [1,2,1,3,5,6,4]
Output: 5
Explanation: 6 is a peak element at index 5. Index 1 (value 2) is also a valid answer.
Example 3
Input: nums = [1]
Output: 0
Explanation: Since nums[-1] and nums[1] are both -∞, nums[0] = 1 is a peak.
Constraints
- -1 <= nums.length <= 1000
- --2^31 <= nums[i] <= 2^31 - 1
- -nums[i] != nums[i + 1] for all valid i.
Optimal Complexity
Time
O(log n)
Space
O(1)
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