46. Permutations

Author: coderbean

pom.xml

@@ -8,5 +8,18 @@
     <artifactId>LeetCode-Java</artifactId>
     <version>1.0-SNAPSHOT</version>
 
-    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>2.3.2</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                    <encoding>UTF-8</encoding>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
 </project>

src/main/java/leetcode/_46_/Main.java

@@ -0,0 +1,19 @@
+package leetcode._46_;
+
+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, 2, 3, 4};
+        System.out.println(solution.permute(nums));
+        System.out.println(solution.permute(nums).size());
+        HashSet<List<Integer>> set = new HashSet<>(solution.permute(nums));
+        System.out.println(set.size());
+    }
+}
+

src/main/java/leetcode/_46_/Solution.java

@@ -0,0 +1,29 @@
+package leetcode._46_;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+class Solution {
+    public List<List<Integer>> permute(int[] nums) {
+        List<List<Integer>> lists = new ArrayList<>();
+        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.permute(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]);
+                lists.add(integers1);
+            }
+        }
+        return lists;
+    }
+}

src/main/java/leetcode/_46_/Xnip2019-07-04_14-30-50.jpg

@@ -0,0 +1,52 @@
+### [46\. Permutations](https://leetcode.com/problems/permutations/)
+
+Difficulty: **Medium**
+
+
+Given a collection of **distinct** integers, return all possible permutations.
+
+**Example:**
+
+```
+Input: [1,2,3]
+Output:
+[
+  [1,2,3],
+  [1,3,2],
+  [2,1,3],
+  [2,3,1],
+  [3,1,2],
+  [3,2,1]
+]
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public List<List<Integer>> permute(int[] nums) {
+        List<List<Integer>> lists = new ArrayList<>();
+        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.permute(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]);
+                lists.add(integers1);
+            }
+        }
+        return lists;
+    }
+}
+```