serialize and deserialize BST

Author: chen0040

.idea/workspace.xml

@@ -384,3 +384,4 @@ codes may not be optimized
 1. [Find K Closest Element](https://leetcode.com/contest/leetcode-weekly-contest-45/problems/find-k-closest-elements/)
 1. [Validate UTF-8](https://leetcode.com/problems/utf-8-validation/description/)
 1. [Kth Smallest Element in a BST](https://leetcode.com/problems/kth-smallest-element-in-a-bst/description/)
+1. [Serialize and Deserialize BST](https://leetcode.com/problems/serialize-and-deserialize-bst/description/)

README.md

@@ -0,0 +1,79 @@
+package com.github.chen0040.leetcode.day18.medium;
+
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+
+/**
+ * Created by xschen on 13/8/2017.
+ *
+ * link: https://leetcode.com/problems/serialize-and-deserialize-bst/description/
+ */
+public class SerializeAndDeserializeBST {
+    public class TreeNode {
+      int val;
+      TreeNode left;
+      TreeNode right;
+      TreeNode(int x) { val = x; }
+  }
+
+   public class Codec {
+
+      // Encodes a tree to a single string.
+      public String serialize(TreeNode root) {
+         StringBuilder sb = new StringBuilder();
+         Queue<TreeNode> queue = new LinkedList<TreeNode>();
+         queue.add(root);
+         boolean first = true;
+         while(!queue.isEmpty()) {
+            TreeNode x = queue.remove();
+            if(first){
+               first = false;
+            } else {
+               sb.append(",");
+            }
+            if(x == null){
+               sb.append("#");
+            } else {
+               sb.append(x.val);
+               queue.add(x.left);
+               queue.add(x.right);
+            }
+         }
+         return sb.toString();
+      }
+
+      // Decodes your encoded data to tree.
+      public TreeNode deserialize(String data) {
+         String[] values = data.split(",");
+         Queue<TreeNode> queue = new LinkedList<TreeNode>();
+
+         int count = 0;
+         TreeNode root = create(values, count++);
+         queue.add(root);
+         while(count < values.length) {
+            TreeNode x = queue.remove();
+            x.left = create(values, count++);
+            x.right = create(values, count++);
+
+            if(x.left != null) {
+               queue.add(x.left);
+            }
+            if(x.right != null) {
+               queue.add(x.right);
+            }
+         }
+         return root;
+      }
+
+      private TreeNode create(String[] values, int count) {
+         if(values[count].equals("#")) {
+            return null;
+         }
+         return new TreeNode(Integer.parseInt(values[count]));
+      }
+
+
+   }
+}