Binary Tree serialization

 

Serialization and deserialization of common Binary Trees:

Traverse in sequence, and the null node is marked with a special symbol.

import java.io.File;import java.io.FileNotFoundException;import java.io.PrintStream;import java.util.Scanner;public class Solution {    public static void serialize(TreeNode root, PrintStream ps) {        if (root == null)            ps.print("# ");        else {            ps.print(root.val + " ");            serialize(root.left, ps);            serialize(root.right, ps);        }    }    public static TreeNode deserialize(Scanner cin) {        String token = cin.next();        if (token.equals("#"))            return null;        int val = Integer.parseInt(token);        TreeNode root = new TreeNode(val);        root.left = deserialize(cin);        root.right = deserialize(cin);        return root;    }    public static void main(String[] args) throws FileNotFoundException {        TreeNode root = new TreeNode(30);        root.left = new TreeNode(20);        root.left.left = new TreeNode(10);        root.right = new TreeNode(40);        root.right.left = new TreeNode(35);        root.right.right = new TreeNode(50);        PrintStream ps = new PrintStream(new File("serialize.txt"));        serialize(root, ps);        Scanner cin = new Scanner(new File("serialize.txt"));        TreeNode back = deserialize(cin);                System.out.println(back.val);    }}

 

 

BST serialization and deserialization:

Serialization: directly first traverse the output

Deserialization: it is constructed by first-order traversal. O (n) time.

import java.io.FileNotFoundException;import java.util.Scanner;public class Solution {    private static int curVal;    public static TreeNode deserializeBSTfromInorder(Scanner cin) {        if (!cin.hasNext())            return null;        else {            curVal = cin.nextInt();            return deserialize(cin, Integer.MIN_VALUE, Integer.MAX_VALUE);        }    }    private static TreeNode deserialize(Scanner cin, int min, int max) {        if (curVal > min && curVal < max) {            int val = curVal;            TreeNode root = new TreeNode(val);            if (cin.hasNext()) {                curVal = cin.nextInt();                root.left = deserialize(cin, min, val);                root.right = deserialize(cin, val, max);            }            return root;        } else            return null;    }    public static void main(String[] args) throws FileNotFoundException {        String s = "30 20 10 40 35 50";        Scanner cin = new Scanner(s);        TreeNode back = deserializeBSTfromInorder(cin);        System.out.println(back.val);    }}

 

From array level data:

public class Solution {    private int curr;    public TreeNode deserialize(int[] preorder) {        curr = 0;        return deserialize(preorder, Integer.MIN_VALUE, Integer.MAX_VALUE);    }    public TreeNode deserialize(int[] preorder, int min, int max) {        if (curr >= preorder.length || preorder[curr] <= min || preorder[curr] >= max) {            return null;        }        int val = preorder[curr++];        TreeNode root = new TreeNode(val);        root.left = deserialize(preorder, min, val);        root.right = deserialize(preorder, val, max);        return root;    }            public static void main(String[] args) {        int[] pre = new int[] { 30, 20, 10, 40, 35, 50 };        TreeNode root = new Solution().deserialize(pre);                System.out.println(root);    }}

 

Refer:

Http://leetcode.com/2010/09/saving-binary-search-tree-to-file.html

Http://leetcode.com/2010/09/serializationdeserialization-of-binary.html

Binary Tree serialization