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55 lines
1.6 KiB
Python
55 lines
1.6 KiB
Python
def max_product_subarray(numbers: list[int]) -> int:
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"""
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Returns the maximum product that can be obtained by multiplying a
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contiguous subarray of the given integer list `numbers`.
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Example:
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>>> max_product_subarray([2, 3, -2, 4])
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6
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>>> max_product_subarray((-2, 0, -1))
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0
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>>> max_product_subarray([2, 3, -2, 4, -1])
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48
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>>> max_product_subarray([-1])
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-1
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>>> max_product_subarray([0])
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0
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>>> max_product_subarray([])
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0
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>>> max_product_subarray("")
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0
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>>> max_product_subarray(None)
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0
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>>> max_product_subarray([2, 3, -2, 4.5, -1])
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Traceback (most recent call last):
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...
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ValueError: numbers must be an iterable of integers
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>>> max_product_subarray("ABC")
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Traceback (most recent call last):
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...
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ValueError: numbers must be an iterable of integers
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"""
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if not numbers:
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return 0
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if not isinstance(numbers, (list, tuple)) or not all(
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isinstance(number, int) for number in numbers
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):
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raise ValueError("numbers must be an iterable of integers")
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max_till_now = min_till_now = max_prod = numbers[0]
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for i in range(1, len(numbers)):
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# update the maximum and minimum subarray products
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number = numbers[i]
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if number < 0:
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max_till_now, min_till_now = min_till_now, max_till_now
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max_till_now = max(number, max_till_now * number)
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min_till_now = min(number, min_till_now * number)
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# update the maximum product found till now
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max_prod = max(max_prod, max_till_now)
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return max_prod
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