/*
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
click to show hints.
Hints:
If you notice carefully in the flattened tree, each node's right
child points to the next node of a pre-order traversal.
*/
/**
* 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 {
private:
TreeNode* pre=NULL;
public:
void flatten(TreeNode* root) {
if(!root) return;
flatten(root->right);
flatten(root->left);
root->left=NULL;
root->right=pre;
pre=root;
}
};
114. Flatten Binary Tree to Linked List
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