Python/dynamic_programming/max_product_subarray.py
Rohan Anand a00492911a
added a problem on kadane's algo and its solution. (#8569)
* added kadane's algorithm directory with one problem's solution.

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* Rename kaadne_algorithm/max_product_subarray.py to dynamic_programming/max_product_subarray.py

* Update dynamic_programming/max_product_subarray.py

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* Update max_product_subarray.py

* Update max_product_subarray.py

* Update dynamic_programming/max_product_subarray.py

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* Update max_product_subarray.py

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* Update max_product_subarray.py

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* Update max_product_subarray.py

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* Update max_product_subarray.py

* Update max_product_subarray.py

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* Update dynamic_programming/max_product_subarray.py

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* Update max_product_subarray.py

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Co-authored-by: Christian Clauss <cclauss@me.com>
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2023-03-31 13:17:13 +02:00

54 lines
1.6 KiB
Python

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