剑指 Offer 32 - I. 从上到下打印二叉树

今天药忘吃喽~ 2022-12-23 11:18 189阅读 0赞

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题目描述

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题目解析

层次遍历

/**
 * 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];
        }
        List<Integer> list = new LinkedList<>();
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()){
            int size = queue.size();
            for (int i = 0; i < size; i++){
                TreeNode pop = queue.poll();
                list.add(pop.val);
                if (pop.left != null){
                    queue.offer(pop.left);
                }
                if (pop.right != null){
                    queue.offer(pop.right);
                }
            }
        }
        int [] ints = new int[list.size()];
        for (int i = 0; i < list.size(); i++){
            ints[i] = list.get(i);
        }
        return ints;
    }
}