Leetcode[tree]: Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place.
For example,
Given
1
/ \
2 5
/ \ \
3 4 6
The flattened tree should look like:
1
\
2
\
3
\
4
\
5
\
6

Recursive algorithm

This kind of problem is very suitable to do with recursion, each time to complete a node conversion, the rest of the things left to do. The problem that needs to be dealt with here is that you need to connect the right subtree of the current node to the last node of the left subtree for the previous sequence traversal.

My C + + code is implemented as follows:

void Flatten (TreeNode *root) {    if (!root) return;    if (root->left) {        TreeNode *pcurnode = root->left;        if (root->right) {while            (pcurnode->right) Pcurnode = pcurnode->right;            Pcurnode->right = root->right;        }        Root->right = root->left;        Root->left = nullptr;    }    Flatten (root->right);}

Iterative algorithm

Very similar to the above, the principle is the same, my C + + code implementation is as follows:

void Flatten (TreeNode *root) {for    (TreeNode *pcurchildroot = root; Pcurchildroot! = nullptr; pcurchildroot = Pcurchil Droot->right)        if (pcurchildroot->left) {            TreeNode *pcurnode = pcurchildroot->left;            if (pcurchildroot->right) {while                (pcurnode->right) Pcurnode = pcurnode->right;                Pcurnode->right = pcurchildroot->right;            }            Pcurchildroot->right = pcurchildroot->left;            Pcurchildroot->left = nullptr;        }}

Leetcode[tree]: Flatten Binary Tree to Linked List