47. Permutations II

Author: coderbean

src/main/java/leetcode/_47_/Main.java

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+package leetcode._47_;
+
+import java.util.HashSet;
+import java.util.List;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        int[] nums = {1, 1, 2};
+        System.out.println(solution.permuteUnique(nums));
+        System.out.println(solution.permuteUnique(nums).size());
+        HashSet<List<Integer>> set = new HashSet<>(solution.permuteUnique(nums));
+        System.out.println(set.size());
+    }
+}
+

src/main/java/leetcode/_47_/Solution.java

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+package leetcode._47_;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+class Solution {
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        List<List<Integer>> lists = new ArrayList<>();
+        Set<List<Integer>> listSet = new HashSet<>();
+        if (nums.length == 0) {
+            return lists;
+        }
+        if (nums.length == 1) {
+            List<Integer> item = new ArrayList<>();
+            item.add(nums[0]);
+            lists.add(item);
+            return lists;
+        }
+        List<List<Integer>> permute = this.permuteUnique(Arrays.copyOfRange(nums, 1, nums.length));
+        for (List<Integer> integers : permute) {
+            for (int i = 0; i <= integers.size(); i++) {
+                ArrayList<Integer> integers1 = new ArrayList<>(integers);
+                integers1.add(i, nums[0]);
+                if (!listSet.contains(integers1)) {
+                    lists.add(integers1);
+                    listSet.add(integers1);
+                }
+            }
+        }
+        return lists;
+    }
+}

src/main/java/leetcode/_47_/solution.md

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+### [47\. Permutations II](https://leetcode.com/problems/permutations-ii/)
+
+Difficulty: **Medium**
+
+
+Given a collection of numbers that might contain duplicates, return all possible unique permutations.
+
+**Example:**
+
+```
+Input: [1,1,2]
+Output:
+[
+  [1,1,2],
+  [1,2,1],
+  [2,1,1]
+]
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        List<List<Integer>> lists = new ArrayList<>();
+        Set<List<Integer>> listSet = new HashSet<>();
+        if (nums.length == 0) {
+            return lists;
+        }
+        if (nums.length == 1) {
+            List<Integer> item = new ArrayList<>();
+            item.add(nums[0]);
+            lists.add(item);
+            return lists;
+        }
+        List<List<Integer>> permute = this.permuteUnique(Arrays.copyOfRange(nums, 1, nums.length));
+        for (List<Integer> integers : permute) {
+            for (int i = 0; i <= integers.size(); i++) {
+                ArrayList<Integer> integers1 = new ArrayList<>(integers);
+                integers1.add(i, nums[0]);
+                if (!listSet.contains(integers1)) {
+                    lists.add(integers1);
+                    listSet.add(integers1);
+                }
+            }
+        }
+        return lists;
+    }
+}
+```