Find the Peak

Difficulty: 1400 3000 ms 128 MB

binary-search

The array strictly increases to a single peak and then strictly decreases (either side may be empty). Print the 1-based index of the peak.

Input: the first line has N; the second line has the mountain array.

Output: the peak's position.

Constraints:

• 1 ≤ N ≤ 10⁵

Sample Tests

5
1 3 5 4 2

3

3
3 2 1

1

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