标签：iter val value etc put solution des while input
Given a binary tree, return the preorder traversal of its nodes‘ values.
Example:
Input:[1,null,2,3]1 2 / 3 Output:[1,2,3]
Follow up: Recursive solution is trivial, could you do it iteratively?
题目大意：
使用非递归的解法，得到二叉树的前序遍历。
解法：
使用栈来做
java:
class Solution {
public List<Integer> preorderTraversal(TreeNode root) {
List<Integer>res=new ArrayList<Integer>();
Stack<TreeNode>rights=new Stack<>();
while(root!=null){
res.add(root.val);
if(root.right!=null) rights.add(root.right);
root=root.left;
if(root==null&&!rights.empty()) root=rights.pop();
}
return res;
}
}
leetcode [144]Binary Tree Preorder Traversal
标签：iter val value etc put solution des while input
原文地址：https://www.cnblogs.com/xiaobaituyun/p/10738809.html
