#coding=utf-8

#Given a collection of distinct numbers, return all possible permutations.

#For example
#[1,2,3] have the following permutations
#[
#[1,2,3],
#[1,3,2],
#[2,1,3],
#[2,3,1],
#[3,1,2],
#[3,2,1]
#]

