Create permutation-nos.md

Author: iMagesh

problems/permutation-nos.md

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+Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order.
+
+ 
+
+Example 1:
+```
+Input: nums = [1,1,2]
+Output:
+[[1,1,2],
+ [1,2,1],
+ [2,1,1]]
+ ```
+Example 2:
+```
+Input: nums = [1,2,3]
+Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
+ ```
+
+Constraints:
+```
+1 <= nums.length <= 8
+-10 <= nums[i] <= 10
+```