Permutations

Question

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]
]

Tags

• Backtracking

Thought

Use backtracking to traversal all possible solutions.

Code

class Solution(object):
    def permute(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        # http://www.cnblogs.com/zuoyuan/p/3758816.html
        if len(nums) == 0: return []
        if len(nums) == 1: return [nums]
        res = []
        for i in range(len(nums)):
            for j in self.permute(nums[:i] + nums[i + 1:]):
                res.append([nums[i]] + j)
        return res