LeetCode/129.cpp at main · rkibel/LeetCode · GitHub

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/**
 * 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) {}
 * };
 */
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 Problem129 {
public:
    int sumNumbers(TreeNode* root) {
        return dfs(root, 0);
    }
    int dfs(TreeNode * root, int cur){
        if (!root)
            return 0;
        cur = cur*10 + root->val;
        if (!root->left && !root->right)
            return cur;
        return dfs(root->left, cur) + dfs(root->right, cur);
    }
};