给定一个二叉树,原地将它展开为链表。
例如,给定二叉树
1
/ \
2 5
/ \ \
3 4 6
将其展开为:
1
\
2
\
3
\
4
\
5
\
6
解题思路:
按照前序遍历的顺序(栈),展开成链表
Java代码:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public void flatten(TreeNode root) {
if(null == root)
return;
Stack<TreeNode> stack = new Stack<>();
TreeNode p = root;
while(null != p.left || null != p.right){
if(null != p.left && null != p.right)
stack.push(p.right);
if(null != p.left){
p.right = p.left;
p.left = null;
}
p = p.right;
}
while(!stack.isEmpty()){
TreeNode tmp = stack.pop();
p.right = tmp;
p = p.right;
while(null != p.left || null != p.right){
if(null != p.left && null != p.right)
stack.push(p.right);
if(null != p.left){
p.right = p.left;
p.left = null;
}
p = p.right;
}
}
}
}