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。
Java实现
import java.util.ArrayList;
import java.util.LinkedList;
class TreeNode {
int val;
TreeNode left;
TreeNode right;
public TreeNode(int val) {
this.val = val;
}
}
public class Solution {
public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
LinkedList<TreeNode> queue = new LinkedList<>();
ArrayList<Integer> ret = new ArrayList<>();
queue.addLast(root);
while (!queue.isEmpty()) {
int cnt = queue.size();
while (cnt-- > 0) {
TreeNode t = queue.removeFirst();
if (t == null)
continue;
ret.add(t.val);
queue.addLast(t.left);
queue.addLast(t.right);
}
}
return ret;
}
}
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