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51 lines
1.3 KiB
Python
51 lines
1.3 KiB
Python
def permute(nums: list[int]) -> list[list[int]]:
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"""
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Return all permutations.
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>>> from itertools import permutations
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>>> numbers= [1,2,3]
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>>> all(list(nums) in permute(numbers) for nums in permutations(numbers))
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True
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"""
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result = []
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if len(nums) == 1:
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return [nums.copy()]
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for _ in range(len(nums)):
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n = nums.pop(0)
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permutations = permute(nums)
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for perm in permutations:
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perm.append(n)
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result.extend(permutations)
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nums.append(n)
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return result
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def permute2(nums):
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"""
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Return all permutations of the given list.
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>>> permute2([1, 2, 3])
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[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 2, 1], [3, 1, 2]]
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"""
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def backtrack(start):
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if start == len(nums) - 1:
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output.append(nums[:])
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else:
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for i in range(start, len(nums)):
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nums[start], nums[i] = nums[i], nums[start]
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backtrack(start + 1)
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nums[start], nums[i] = nums[i], nums[start] # backtrack
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output = []
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backtrack(0)
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return output
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if __name__ == "__main__":
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import doctest
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# use res to print the data in permute2 function
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res = permute2([1, 2, 3])
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print(res)
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doctest.testmod()
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