Find Peak Element - ELI5 Park

👶 The 5-Year-Old Summary

Find a mountain peak in an array! A peak is bigger than its neighbors. You can see the whole array - find any peak quickly!

🎮 Interactive Visualizer

Array: [1, 2, 3, 1]

🧠 The Brain Hack

If nums[mid] < nums[mid+1], there's a peak on the RIGHT side! Go there! Otherwise, the peak is on the LEFT (or at mid)!

💻 The Clean Solution

def find_peak(nums):
    left, right = 0, len(nums) - 1
    
    while left < right:
        mid = (left + right) // 2
        
        # If going up, peak is to the right
        if nums[mid] < nums[mid + 1]:
            left = mid + 1
        # Otherwise, peak is here or to left
        else:
            right = mid
    
    return left  # Or right, they're the same!

# [1, 2, 3, 1] → peak at index 2 (value 3)

Time: O(log n)

Space: O(1)