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
If you notice carefully in the flattened tree, each node‘s right child points to the next node of a pre-order traversal.
空间消耗比较大，非in-place的解法。
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public void flatten(TreeNode root) {
if(root==null) return;
ArrayList<TreeNode> a=new ArrayList<TreeNode>();
prevOrder(root,a);
for(int i=0;i<a.size()-1;i++){
a.get(i).left=null;
a.get(i).right=a.get(i+1);
}
}
public void prevOrder (TreeNode root,List<TreeNode> a){
if(root==null) return;
a.add(root);
prevOrder(root.left,a);
prevOrder(root.right,a);
}
}改进的解法/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public void flatten(TreeNode root) {
if(root==null) return;
while(root!=null){
if(root.left!=null){
TreeNode node=root.left;
while(node.right!=null) node=node.right;
node.right=root.right;
root.right=root.left;
root.left=null;
}
root=root.right;
}
}
}
Flatten Binary Tree to Linked List,布布扣,bubuko.com
Flatten Binary Tree to Linked List
原文地址：http://blog.csdn.net/dutsoft/article/details/38611431
