Permutations Generation

Problem

Generate every permutation of the integers in nums and return them as a list of lists in lexicographic order.

Backtrack over a sorted copy of the input, tracking which positions are already used, and append each completed arrangement. The input may be unsorted; return a list containing only the empty list when nums is empty.

Hint

Sort a copy first, then choose elements position by position with a used flag.

Test cases

case 1

in: [[1,2,3]]

expected: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

case 2

in: [[0]]

expected: [[0]]

case 3

in: [[]]

expected: [[]]

case 4

in: [[3,1,2]]

expected: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Starter codePython

def permutations(nums):
    # Your code here
    pass

4 test cases · run your code against them in the editor