文章作者：Tyan 部落格：noahsnail.com  |  CSDN  |  簡書

1. Description

2. Solution

/**
 * 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 sum = 0;
        traverseSum(root, sum, 0);
        return sum;
    }

private:
    void traverseSum(TreeNode* root, int& sum, int current) {
        current = current * 10 + root->val;
        if(!root->left &&
 
 !root->right) {
            sum += current;
            return;
        }
        if(root->left) {
            traverseSum(root->left, sum, current);
        }
        if(root->right) {
            traverseSum(root->right, sum, current);
        }
    }
};

Reference