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44 lines
1.0 KiB
Python
44 lines
1.0 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# author: bt3gl
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'''
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Given an array of integers arr, return true if and only if it is a valid mountain array.
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Recall that arr is a mountain array if and only if:
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arr.length >= 3
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There exists some i with 0 < i < arr.length - 1 such that:
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arr[0] < arr[1] < ... < arr[i - 1] < arr[i]
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arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
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'''
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def valid_mountain_array(arr: list[int]) -> bool:
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last_number, mountain_up = arr[0], True
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for i, n in enumerate(arr[1:]):
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if n > last_number:
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if mountain_up == False:
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return False
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elif n < last_number:
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if i == 0:
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return False
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mountain_up = False
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else:
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return False
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last_number = n
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return not mountain_up
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if __name__ == "__main__":
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arr = [0,3,2,1]
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print(valid_mountain_array(arr))
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