Create 46_Permutations.md

Author: koji

46_Permutations.md

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+## 46. Permutations
+
+Given a collection of distinct integers, return all possible permutations.
+
+Example:
+
+Input: [1,2,3]
+Output:
+[
+ [1,2,3],
+ [1,3,2],
+ [2,1,3],
+ [2,3,1],
+ [3,1,2],
+ [3,2,1]
+]
+
+```python
+def permute(self, nums: List[int]) -> List[List[int]]:
+ result = []
+ if len(nums) ==0: return result
+
+ def gen_pattern(build, index):
+ if len(nums) == index:
+ result.append(build)
+ return
+ 
+ for num in nums:
+ if not num in build: 
+ gen_pattern(build+[num], index+1)
+ 
+ gen_pattern([], 0)
+ return result
+```
+
+
+```
+Runtime: 36 ms, faster than 86.09% of Python3 online submissions for Permutations.
+Memory Usage: 14.3 MB, less than 100.00% of Python3 online submissions for Permutations.
+```