LIKE CODING: LeetCode [297] Serialize and Deserialize Binary Tree

297. Serialize and Deserialize Binary Tree

Hard

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.

Clarification: The input/output format is the same as how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Example 1:

Input: root = [1,2,3,null,null,4,5]
Output: [1,2,3,null,null,4,5]

Example 2:

Input: root = []
Output: []

Example 3:

Input: root = [1]
Output: [1]

Example 4:

Input: root = [1,2]
Output: [1,2]

Constraints:

The number of nodes in the tree is in the range [0, 104].
-1000 <= Node.val <= 1000

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Codec {
    void serialize(TreeNode* node, stringstream &ss){
        if(!node)
        {
            ss<<"# ";
        }
        else
        {
            ss<<node->val<<" ";
            serialize(node->left, ss);
            serialize(node->right, ss);
        }
    }
    
    TreeNode* deserialize(stringstream &ss)
    {
        string s;
        ss>>s;
        if(s=="#"){
            return NULL;
        }else{
            TreeNode* node = new TreeNode(stoi(s));
            node->left = deserialize(ss);
            node->right = deserialize(ss);
            return node;
        }
    }
public:

    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        stringstream ss;
        serialize(root, ss);
        return ss.str();
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        stringstream ss;
        ss<<data;
        return deserialize(ss);
    }
};

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

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Codec {
    String str;
    String[] strs;
    int index = 0;
    // Encodes a tree to a single string.
    public String serialize(TreeNode root) {
        str = "";
        sh(root);
        return str;
    }
    
    void sh(TreeNode node){
        if(str.length()>0) str += ",";
        if(node==null){
            str += "#";
        }else{
            str += node.val;
            sh(node.left);
            sh(node.right);
        }
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        strs = data.split(",");
        index = 0;
        return dh();
    }
    
    TreeNode dh(){
        TreeNode node;
        String s = strs[index++];
        if(s.equals("#")){
            node = null;
        }else{
            node = new TreeNode(Integer.parseInt(s));
            node.left = dh();
            node.right = dh();
        }
        return node;
    }
}

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

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Monday, October 26, 2015

LeetCode [297] Serialize and Deserialize Binary Tree

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