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Nenogzar

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Aug 22nd, 2023
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  1.  
  2. def permute(nums):
  3. """
  4. Return all permutations of the given list.
  5. >>> permute([1, 2, 3])
  6. [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 2, 1], [3, 1, 2]]
  7. """
  8. def backtrack(start):
  9. """
  10. Generate permutations by recursively swapping elements.
  11. """
  12. if start == len(nums) - 1:
  13. output.append(nums[:])
  14. else:
  15. for i in range(start, len(nums)):
  16. nums[start], nums[i] = nums[i], nums[start]
  17. backtrack(start + 1)
  18. # backtrack
  19. nums[start], nums[i] = nums[i], nums[start]
  20.  
  21. output = []
  22. backtrack(0)
  23. return output
  24.  
  25.  
  26. # input the list from keyboard
  27. while True:
  28. input_str = input("enter a list of numbers separated by commas: ")
  29. nums = [int(x) for x in input_str.split(',') if x.strip().isdigit()]
  30.  
  31. if nums:
  32. break
  33. else:
  34. print("Invalid input. Please, try again.")
  35.  
  36. res = permute(nums)
  37. print(f"Permutations of the list {nums} are: {res}")
  38.  
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