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Find Peak Element

Medium

Climb toward the higher neighbour

In simple words

A peak is bigger than both neighbors; always step toward the higher side and you'll climb to one.

The idea

If mid is on an upward slope the peak is to the right, otherwise to the left. Follow the ascent and you always converge on a peak.

1
2
1
3
5
6
4
0
1
2
3
4
5
6

Step 1 of 4. Brute force: scan for any element ≥ both of its neighbours. Values: 1, 2, 1, 3, 5, 6, 4.

1/4
Brute force
timeO(n)spaceO(1)

Scan for a peak.

1let peak = -1;2for (let i = 0; i < n && peak < 0; i++)3  if (nums[i] >= left && nums[i] >= right) peak = i;4return peak;

Input

array
[1, 2, 1, 3, 5, 6, 4]

Memory

i
—

Output

answer
—

Check yourself

3 quick questions about this walkthrough. A wrong answer costs nothing.

Examples

Example 1

Input:
nums = [1, 2, 3, 1]
Output:
2
Explanation:
3 at index 2 is bigger than both neighbours.

Example 2

Input:
nums = [1, 2, 1, 3, 5, 6, 4]
Output:
5
Explanation:
Index 5 (value 6) is a peak.

Example 3

Input:
nums = [1, 2, 3]
Output:
2
Explanation:
The last, biggest element is a peak.

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