47. Permutations II

https://leetcode.com/problems/permutations-ii/

Python

Use Python itertools.permutations

from itertools import permutations

class Solution:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        return set([perm for perm in permutations(nums)])

Backtracking

from itertools import permutations

class Solution:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        result = set()

        def backtracking(track: list, used: set):
            if len(track) == len(nums):
                result.add(tuple(track))
                return

            for i, num in enumerate(nums):
                if i in used:
                    continue
                used.add(i)
                track.append(num)

                backtracking(track, used)

                used.remove(i)
                track.pop()

        backtracking([], set())
        return result

Javascript

var permuteUnique = function(nums) {
  const result = [];
   var backtrack = function(hashmap, record =[]) {
     // base case: the length of array has reached the length of nums
     if (record.length === nums.length) {
       result.push(record.slice());
       return;
     }

     // use hashmap to memorize the number which had traversed
     for (let key in hashmap) {
       if (hashmap[key] <= 0) continue;
       hashmap[key] -= 1;
       record.push(Number(key));
       backtrack(hashmap, record);
       hashmap[key] += 1;
       record.pop();

     }
   }

   const hashmap = nums.reduce((acc, num) => {
     if (acc[num] !== undefined) acc[num] += 1;
     else acc[num] = 1;
     return acc;
   }, {})

   backtrack(hashmap)
   return result;
};