从上往下打印二叉树
题目描述
从上往下打印出二叉树的每个节点,同层节点从左至右打印。
AC代码
import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
/**
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
}
*/
public class Solution {
public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
ArrayList<Integer> list = new ArrayList<Integer>();
Deque<TreeNode> deque = new LinkedList<TreeNode>();
if(root == null)
return list;
deque.add(root);
while(!deque.isEmpty()){
TreeNode temp = deque.pop();
list.add(temp.val);
if(temp.left != null)
deque.add(temp.left);
if(temp.right != null)
deque.add(temp.right);
}
return list;
}
}