Permutations.py

import copy
# Given a collection of distinct integers, return all possible permutations.

# Example:

# Input: [1,2,3]
# Output:
# [
#   [1,2,3],
#   [1,3,2],
#   [2,1,3],
#   [2,3,1],
#   [3,1,2],
#   [3,2,1]
# ]

def permutation_recursive(nums, path):
#### Base case return [combination] list of list
# for example [[1,2,3]]+[[2,3,4]] =>> [[1,2,3],[2,3,4]]
    if len(nums) == 0:
        return [path]

    output = []

    for i in range(len(nums)):
        copy_path = copy.deepcopy(path)
        copy_path.append(nums[i])
        permutations = permutation_recursive(nums[:i] + nums[i + 1:], copy_path)

        output += permutations

    return output

def permute(nums):
    return permutation_recursive(nums, [])

print(permute([1, 2, 3]))

[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]