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.
前序遍历，按访问序往右加就行了。
需要注意的是，加入单链之后要删掉原先的子女链接。
/**
* 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) {
if(!root)
return; TreeNode* newtail = new TreeNode(-);
stack<TreeNode*> stk;
stk.push(root);
while(!stk.empty())
{
TreeNode* top = stk.top();
newtail->right = top;
newtail = newtail->right;
stk.pop(); if(top->right)
stk.push(top->right);
if(top->left)
stk.push(top->left); top->left = NULL;
top->right = NULL;
}
}
};