Fork me on GitHub

Flatten Binary Tree to Linked List

Posted on

Description

https://leetcode.com/problems/flatten-binary-tree-to-linked-list/description/

Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
/**
 * 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:
    void flatten(TreeNode* root) {
        if (root == NULL) return;
        this->transform(root);
    }
    TreeNode* transform(TreeNode* root) {
        TreeNode* temp = root->right;
        TreeNode* current = root;
        if (root->left != NULL) {
            root->right = root->left;
            current = this->transform(root->left);
            current->left = NULL;
            root->left = NULL;
            current->right = temp;
        }
        if (temp == NULL) return current;
        current = this->transform(temp);
        return current;
    }
};