Sat May 6 01:33:00 UTC 2023 inscode

Main.java

-class Main {
+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class Main {
   public static void main(String[] args) {
-    System.out.println("Hello world!");
+    
+    int[] arr = {1, 2, 3};
+        ArrayList<ArrayList<Integer>> result = Permutations.permute(arr);
+        System.out.println(result);
   }
 }
\ No newline at end of file

Permutations.java

+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class Permutations {
+    public static void main(String[] args) {
+        int[] arr = {1, 2, 3};
+        ArrayList<ArrayList<Integer>> result = permute(arr);
+        System.out.println(result);
+    }
+
+    public static ArrayList<ArrayList<Integer>> permute(int[] nums) {
+        ArrayList<ArrayList<Integer>> result = new ArrayList<>();
+        if (nums == null || nums.length == 0) {
+            return result;
+        }
+        ArrayList<Integer> list = new ArrayList<Integer>();
+        Arrays.sort(nums);
+        boolean[] used = new boolean[nums.length];
+        helper(result, list, nums, used);
+        return result;
+    }
+
+    public static void helper(ArrayList<ArrayList<Integer>> result, ArrayList<Integer> list, int[] nums, boolean[] used) {
+        if (list.size() == nums.length) {
+            result.add(new ArrayList<Integer>(list));
+            return;
+        }
+        for (int i = 0; i < nums.length; i++) {
+            if (used[i] || (i > 0 && nums[i] == nums[i - 1] && !used[i - 1])) {
+                continue;
+            }
+            used[i] = true;
+            list.add(nums[i]);
+            helper(result, list, nums, used);
+            used[i] = false;
+            list.remove(list.size() - 1);
+        }
+    }
+}