Find Peak Element
A peak element is an element that is strictly greater than its neighbors.
Given an integer array nums, find a peak element and return its index.
You may imagine that nums[-1] = nums[n] = -∞.
This means an element can be a peak even if it is at the beginning or end of the array.
You must solve the problem in O(log n) time.
Example 1
Input
n = 4 nums = [1, 2, 3, 1]
Output
2
Explanation
nums[2] = 3 is greater than both of its neighbors:
2 < 3 > 1
Therefore, index 2 is a peak.
Example 2
Input
n = 5 nums = [1, 2, 1, 3, 5]
Output
1
Explanation
nums[1] = 2 is a peak because:
1 < 2 > 1
Index 1 is therefore a valid answer.
Constraints
Hints:
Hint 1
Compare the middle element with the element immediately to its right.
Hint 2
If:
nums[mid] < nums[mid + 1]
then a peak must exist somewhere to the right.
Otherwise, a peak exists at mid or somewhere to the left.
Author & Technical Reviewer
Technically reviewed by: ExamAdda Technical Review Team
Technical Reviewers, ExamAdda
Software engineers at ExamAdda who check every article's definitions, complexity claims and code examples before and after publishing.
Published
Aug 22, 2026
Last updated
Sep 15, 2026
Content Verification Methodology
Definitions and complexity claims were checked against authoritative computer-science references. Code examples were compiled and tested with standard, boundary and edge-case inputs.
Expected Output