Description

Submission

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
    int ret;
    
    void dfs(TreeNode* cur, int val) {
        if(!cur) return;
        if(cur->left == nullptr && cur->right == nullptr) {
            ret += val * 10 + cur->val;
            return;
        }
        int newVal = val * 10 + cur->val;
        dfs(cur->left, newVal);
        dfs(cur->right, newVal);
    }
public:
    int sumNumbers(TreeNode* root) {
        ret = 0;
        dfs(root, 0);
        return ret;
    }
};