LeetCode 129. Sum Root to Leaf Numbers (javascript)

You are given the root of a binary tree containing digits from 0 to 9 only.

Each root-to-leaf path in the tree represents a number.

For example, the root-to-leaf path 1 -> 2 -> 3 represents the number 123.

Return the total sum of all root-to-leaf numbers.

A leaf node is a node with no children.

Example 1:

Input: root = [1,2,3]
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.

Example 2:

Input: root = [4,9,0,5,1]
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.

Constraints:

The number of nodes in the tree is in the range [1, 1000].
0 <= Node.val <= 9
The depth of the tree will not exceed 10.

Idea:

Use DFS Template

Solution 1:

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var sumNumbers = function(root) {
    if (root === null) return;
    let res = [];
    let cur = [];
    dfs(root, res, cur);
    let sum = 0;
    for (let num of res) {
        sum += num;
    }
    return sum;
};

function dfs(root, res, cur) {
    // exit recursion:
    if (root === null) return;
    // found leaf, save the number
    if (root.left === null && root.right === null) {
        cur.push(root.val);
        res.push(parseInt(cur.join('')));
        cur.pop();
        return;
    }
    
    // possible solution
    if (root !== null) {
        cur.push(root.val);
        dfs(root.left, res, cur);
        dfs(root.right, res, cur);
        cur.pop();
    }
    return;
}

Solution 2: (Version 2)

var sumNumbers = function(root) {
    if (root === null) return;
    let res = [0];
    let cur = [0];
    dfs(root, res, cur);
    return res[0];
};

function dfs(root, res, cur) {
    // exit recursion:
    if (root === null) return;
    // found leaf, save the number
    if (root.left === null && root.right === null) {
        cur[0] = cur[0] * 10 + root.val;
        res[0] += cur[0];
        cur[0] = (cur[0] - root.val) / 10;
        return;
    }
    
    // possible solution
    if (root !== null) {
        cur[0] = cur[0] * 10 + root.val;
        dfs(root.left, res, cur);
        dfs(root.right, res, cur);
        cur[0] = (cur[0] - root.val) / 10;
    }
    return;
}