297. Serialize and Deserialize B

二叉树序列化与反序列化

• Runtime: 172 ms, faster than 42.05%
• Memory Usage: 49.5 MB, less than 31.68%

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */

/**
 * Encodes a tree to a single string.
 *
 * @param {TreeNode} root
 * @return {string}
 */
var serialize = function(root) {
    if (!root) return '[]'
    let queue = [root]
    let res = []
    while(queue.length > 0) {
        const node = queue.shift()       
        if(node) {
            res.push(node.val)
            queue.push(node.left)
            queue.push(node.right)
        } else {
            res.push(null)
        }  
    }
    return JSON.stringify(res)
};

/**
 * Decodes your encoded data to tree.
 *
 * @param {string} data
 * @return {TreeNode}
 */
var deserialize = function(data) {
    let res = JSON.parse(data)
    if(res.length === 0) return null
    
    let root = new TreeNode(res.shift())
    let queue = [root]
    for (let i = 0; i < res.length; i++) {
        const node = queue.shift()
        if (res[i] !== null) {
            let left = new TreeNode(res[i])
            node.left = left
            queue.push(left)
        } 
        if (res[++i] !== null) {
            let right = new TreeNode(res[i])
            node.right = right
            queue.push(right)
        } 
    }
    return root
};

/**
 * Your functions will be called as such:
 * deserialize(serialize(root));
 */