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]
]
Solution
这是一道典型的回溯题，通过不断递归即可找到所有解
class Solution(object):
def permute(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
ret = []
def back(nums, p = []):
if not nums:
ret.append(p)
return
for i in range(len(nums)) :
back(nums[:i] + nums[i+1:], p + [nums[i]])
back(nums)
return ret
