Create Permutations II.java

Algorithms/Permutations II.java

@@ -0,0 +1,28 @@
+public class Solution {
+    public List<List<Integer>> permuteUnique(int[] num) {
+        List<List<Integer>> result = new ArrayList<List<Integer>>();
+        if (num.length == 0) return result;
+        boolean[] used = new boolean[num.length];
+        List<Integer> list = new ArrayList<Integer>();
+        Arrays.sort(num);
+        dfs(num, num.length, list, used, result);
+        return result;
+    }
+
+    private void dfs(int[] num, int n, List<Integer> list, boolean[] used, List<List<Integer>> result) {
+        if (list.size() == n) {
+            result.add(new ArrayList<Integer>(list));
+        } else {
+            for (int i = 0; i < n; i++) {
+                if (used[i] == false) {
+                    used[i] = true;
+                    list.add(num[i]);
+                    dfs(num, n, list, used, result);
+                    used[i] = false;
+                    list.remove(list.size() - 1);
+                    while (i < n - 1 && num[i] == num[i+1]) i++;
+                }
+            }
+        }
+    }
+}