From a84eb5c7f2b39b18873583e309181d3762123c63 Mon Sep 17 00:00:00 2001
From: Atousa Duprat <atousa.p@gmail.com>
Date: Wed, 19 May 2021 18:03:43 -0700
Subject: [PATCH] permutation with duplicate

---
 Recursion/PermutationWithDuplicate.java | 46 +++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 Recursion/PermutationWithDuplicate.java

diff --git a/Recursion/PermutationWithDuplicate.java b/Recursion/PermutationWithDuplicate.java
new file mode 100644
index 0000000..47cf062
--- /dev/null
+++ b/Recursion/PermutationWithDuplicate.java
@@ -0,0 +1,46 @@
+import java.util.*;
+
+//leetcode 47 permutation 1, 2
+public class PermutationWithDuplicate {
+
+
+    public static List<List<Integer>> permuteUnique(int[] nums) {
+
+        List<Integer> slate = new ArrayList<>(nums.length);
+        List<List<Integer>> result = new ArrayList<>();
+        permuteHelper(nums, 0, slate, result);
+        return result;
+    }
+
+    public static void permuteHelper(int[] nums, int numsIdx, List<Integer> slate, List<List<Integer>> result) {
+        if (nums.length == numsIdx) {
+            result.add(new ArrayList<>(slate));
+            return;
+        }
+       Set<Integer> m = new HashSet<>();
+        for (int i = numsIdx; i < nums.length; i++) {
+            if (!m.contains(nums[i])) {
+                swap2(nums, i, numsIdx);
+                slate.add(nums[numsIdx]);
+                m.add(nums[numsIdx]);
+                permuteHelper(nums, numsIdx+1, slate, result);
+                swap2(nums, i, numsIdx);
+                slate.remove(slate.size() - 1);
+            }
+        }
+    }
+
+        public static void swap2(int[] nums, int v1, int v2){
+            int temp = nums[v2];
+            nums[v2] = nums[v1];
+            nums[v1] = temp;
+        }
+
+        public static void main (String[]args){
+            int[] a = {1, 1, 2,2};
+            List<List<Integer>> result = permuteUnique(a);
+            System.out.println(result);
+
+        }
+    }
+