Permutations

Given a collection of numbers, return all possible permutations.

Example:

[1,2,3] will have the following permutations:

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

NOTE

• No two entries in the permutation sequence should be the same.
• For the purpose of this problem, assume that all the numbers in the collection are unique.

Warning : DO NOT USE LIBRARY FUNCTION FOR GENERATING PERMUTATIONS.
Example : next_permutations in C++ / itertools.permutations in python.
If you do, we will disqualify your submission retroactively and give you penalty points.

NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a question? Checkout Sample Codes for more details.