# Leetcode: Permutations

Permutations

Similar Problems:

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]
]
```

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

```## Blog link: https://code.dennyzhang.com/permutations
## Basic Ideas: Insertion
##            1
##            12 -> 12; 21
##            123 -> 312, 132, 123; 321, 231, 213
###           1234 -> ...
## Complexity:
import copy
class Solution:
def permute(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
if len(nums) == 0: return [[v]]
return self.myPermute(nums[0:-1], nums[-1])

def myPermute(self, nums, v):
if len(nums) == 0: return [[v]]
res = []
l = self.myPermute(nums[0:-1], nums[-1])
for sequence in l:
for i in range(0, len(sequence)+1):
row = copy.deepcopy(sequence)
row.insert(i, v)
res.append(row)
return res
```

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