Solution32_2.java

package com.usher.algorithm.offer;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;

/**
 * @Author: Usher
 * @Description:
 * 从上到下按层打印二叉树，同一层结点从左至右输出。每一层输出一行。
 */
public class Solution32_2 {
    ArrayList<ArrayList<Integer>> Print(TreeNode pRoot) {
        ArrayList<ArrayList<Integer>> ret = new ArrayList<>();

        if (pRoot == null)
            return ret;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(pRoot);

        while (!queue.isEmpty()){
            ArrayList<Integer> list = new ArrayList<>();
            int size = queue.size();

            for (int i =0;i < size;i++){
                TreeNode node = queue.poll();
                list.add(node.val);

                if (node.left != null)
                    queue.add(node.left);
                if (node.right != null)
                    queue.add(node.right);
            }

            ret.add(list);
        }
        return ret;
    }
}