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程式語言 - LeetCode - CPP - 623. Add One Row to Tree

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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:
    TreeNode* addOneRow(TreeNode* root, int val, int depth) {
        auto dfs = [&](this auto&& dfs, TreeNode* n, int v, int d) -> void {
            if (!n) {
                return;
            }
        
            if (d - 1 == 0) {
                TreeNode *p;

                p = n->left;
                n->left = new TreeNode(val);
                n->left->left = p;

                p = n->right;
                n->right = new TreeNode(val);
                n->right->right = p;
            }

            dfs(n->left, val , d - 1);
            dfs(n->right, val , d - 1);
        };

        if (depth == 1) {
            TreeNode *p = new TreeNode(val);

            p->left = root;
            p->right = nullptr;
            return p;
        }

        dfs(root, val, depth - 1);

        return root;
    }
};