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Leetcode[297] Serialize and Deserialize Binary Tree

05 Dec 2015

###Task1 Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following tree

    1
   / \
  2   3
     / \	     
    4   5

as “[1,2,3,null,null,4,5]”, just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

###Java

/**
 * Definition for a binary tree node.
 * 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();
        buildString(root, sb);
        return sb.toString();
        
    }
    
    public void buildString(TreeNode node, StringBuilder sb) {
        if (node == null) {
            sb.append("null,");
            return;
        }
        sb.append(String.valueOf(node.val) + ",");
        buildString(node.left, sb);
        buildString(node.right, sb);
        return;
        
    }
    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        if (data.equals("")) {
            return null;
        }
        Queue<String> queue = new LinkedList(Arrays.asList(data.split(",")));
        return buildTree(queue);
    }
    
    public TreeNode buildTree(Queue<String> queue) {
        String cur = queue.poll();
        if (cur.equals("null")) {
            return null;
        }
        TreeNode node = new TreeNode(Integer.valueOf(cur));
        node.left = buildTree(queue);
        node.right = buildTree(queue);
        return node;
    }
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));

###Points

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