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59 lines
1.7 KiB
Python
59 lines
1.7 KiB
Python
from __future__ import annotations
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# Divide and Conquer algorithm
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def find_max(nums: list[int | float], left: int, right: int) -> int | float:
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"""
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find max value in list
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:param nums: contains elements
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:param left: index of first element
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:param right: index of last element
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:return: max in nums
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>>> for nums in ([3, 2, 1], [-3, -2, -1], [3, -3, 0], [3.0, 3.1, 2.9]):
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... find_max(nums, 0, len(nums) - 1) == max(nums)
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True
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True
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True
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True
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>>> nums = [1, 3, 5, 7, 9, 2, 4, 6, 8, 10]
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>>> find_max(nums, 0, len(nums) - 1) == max(nums)
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True
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>>> find_max([], 0, 0)
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Traceback (most recent call last):
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...
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ValueError: find_max() arg is an empty sequence
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>>> find_max(nums, 0, len(nums)) == max(nums)
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Traceback (most recent call last):
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...
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IndexError: list index out of range
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>>> find_max(nums, -len(nums), -1) == max(nums)
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True
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>>> find_max(nums, -len(nums) - 1, -1) == max(nums)
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Traceback (most recent call last):
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...
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IndexError: list index out of range
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"""
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if len(nums) == 0:
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raise ValueError("find_max() arg is an empty sequence")
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if (
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left >= len(nums)
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or left < -len(nums)
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or right >= len(nums)
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or right < -len(nums)
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):
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raise IndexError("list index out of range")
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if left == right:
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return nums[left]
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mid = (left + right) >> 1 # the middle
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left_max = find_max(nums, left, mid) # find max in range[left, mid]
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right_max = find_max(nums, mid + 1, right) # find max in range[mid + 1, right]
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return left_max if left_max >= right_max else right_max
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if __name__ == "__main__":
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import doctest
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doctest.testmod(verbose=True)
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