Create Permutations

Author: HarryWangATX

Permutations

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+class Solution {
+    List<List<Integer>> res = new ArrayList<>();
+    public List<List<Integer>> permute(int[] nums) {
+        dfs(nums, new ArrayList<>(), new HashSet<>());
+        return res;
+    }
+    public void dfs(int[] nums, List<Integer> store, Set<Integer> used){
+        if(store.size() == nums.length){
+            res.add(new ArrayList<Integer>(store));
+            return ;
+        }
+        for(int i = 0; i<nums.length; i++){
+            if(used.contains(nums[i])) continue;
+            used.add(nums[i]);
+            store.add(nums[i]);
+            dfs(nums, store, used);
+            store.remove(store.size()-1);
+            used.remove(nums[i]);
+        }
+    }
+}