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
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 binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: void flatten(TreeNode *root) { // Start typing your C/C++ solution below // DO NOT write int main() function TreeNode* tail=root; _flatten(root,tail); } void _flatten(TreeNode*& root,TreeNode*& tail) { if( !root ) return; TreeNode* lhead=root->left,*ltail=root->left; _flatten(lhead,ltail); TreeNode* rhead=root->right,*rtail=root->right; _flatten(rhead,rtail); if ( lhead ) { tail->right=lhead; tail=ltail; } if ( rhead ) { tail->right=rhead; tail=rtail; } root->left=tail->right=NULL; } };