题目
题链：剑指 Offer 32 - I. 从上到下打印二叉树
题解
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大佬详细题解：剑指 Offer 32 - I. 从上到下打印二叉树
/*** Definition for a binary tree node.* public class TreeNode {*int val;*TreeNode left;*TreeNode right;*TreeNode(int x) { val = x; }* }*/class Solution {public int[] levelOrder(TreeNode root) {if (root == null){return new int[0];}ArrayList<Integer> ans = new ArrayList<>();Queue<TreeNode> queue = new LinkedList<>();queue.add(root);while (!queue.isEmpty()){if (queue.peek() != null){ans.add(queue.peek().val);queue.add(queue.peek().left);queue.add(queue.peek().right);}queue.poll();}int[] res = new int[ans.size()];for (int i = 0; i < ans.size(); i++) {res[i] = ans.get(i);}return res;}}
