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程式語言 - LeetCode - C++ - 129. Sum Root to Leaf Numbers

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題目：


解答：

/**
 * 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 {
public:
    int sumNumbers(TreeNode* root) {
        auto dfs = [&](this auto&& dfs, TreeNode *n, int sum) -> int {
            if (!n) {
                return 0;
            }

            sum = n->val + (sum * 10);
            if (!n->left && !n->right) {
                return sum;
            }

            return dfs(n->left, sum) + dfs(n->right, sum);
        };

        return dfs(root, 0);
    }
};