Sum Root to Leaf Numbers Solutions in C++

// Source : https://oj.leetcode.com/problems/sum-root-to-leaf-numbers/
// Author : Hao Chen
// Date   : 2014-06-21



/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int sumNumbers(TreeNode *root) {
    
        if (!root) return 0;
        
        int sum = 0;       
        vector<TreeNode*> v;
        v.push_back(root);
        while(v.size()>0){
            TreeNode* node = v.back();
            v.pop_back();
            if (node->left){
                node->left->val += (10*node->val); 
                v.push_back(node->left);
            }
            if (node->right){
                node->right->val += (10*node->val); 
                v.push_back(node->right);
            }
            if(!node->right && !node->left){
                sum += node->val;
            }
        }
        
        return sum;
    }
};

#include <cstddef>

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
    int sumNumbers(TreeNode *root) {
        return sumNumbers(root, 0);
    }
private:
    int sumNumbers(TreeNode *root, int sum)
    {
        if (!root) return 0;
        else if (!root->left && !root->right) return sum + root->val;
        else return sumNumbers(root->left, (root->val + sum) * 10) + sumNumbers(root->right, (root->val + sum) * 10);
    }
};

/// Source : https://leetcode.com/problems/sum-root-to-leaf-numbers/description/
/// Author : liuyubobobo
/// Time   : 2018-10-16

#include <iostream>

using namespace std;


/// Recursion
/// Time Complexity: O(n)
/// Space Complexity: O(logn)

/// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
    int sumNumbers(TreeNode* root) {

        if(!root) return 0;

        int res = 0;
        dfs(root, 0, res);
        return res;
    }

private:
    void dfs(TreeNode* node, int tnum, int& sum){

        tnum = tnum * 10 + node->val;

        if(!node->left && !node->right)
            sum += tnum;
        else{
            if(node->left)
                dfs(node->left, tnum, sum);
            if(node->right)
                dfs(node->right, tnum, sum);
        }
    }
};


int main() {

    return 0;
}