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Update permutations.py #8102

Merged
merged 11 commits into from
May 31, 2023
26 changes: 25 additions & 1 deletion data_structures/arrays/permutations.py
Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
def permute(nums: list[int]) -> list[list[int]]:
"""
Return all permutations.

>>> from itertools import permutations
>>> numbers= [1,2,3]
>>> all(list(nums) in permute(numbers) for nums in permutations(numbers))
Expand All @@ -20,7 +19,32 @@ def permute(nums: list[int]) -> list[list[int]]:
return result


def permute2(nums):
"""
Return all permutations of the given list.

>>> permute2([1, 2, 3])
[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 2, 1], [3, 1, 2]]
"""

def backtrack(start):
if start == len(nums) - 1:
output.append(nums[:])
else:
for i in range(start, len(nums)):
nums[start], nums[i] = nums[i], nums[start]
backtrack(start + 1)
nums[start], nums[i] = nums[i], nums[start] # backtrack

output = []
backtrack(0)
return output


if __name__ == "__main__":
import doctest

# use res to print the data in permute2 function
res = permute2([1, 2, 3])
print(res)
doctest.testmod()