剑指offer-60-二叉树打印成行

思路

用Queue保存一行结点，每次遍历一整行

代码

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

public class Solution {
    ArrayList<ArrayList<Integer>> Print(TreeNode pRoot){
        ArrayList<ArrayList<Integer>> result = new ArrayList<>();
        if(pRoot==null){
            return result;
        }
        Queue<TreeNode> q = new LinkedList<>();
        q.add(pRoot);
        while (!q.isEmpty()) {
            ArrayList<Integer> temp = new ArrayList<>();
            Queue<TreeNode> tempQ = new LinkedList<>();
            while (!q.isEmpty()) {
                TreeNode t = q.poll();
                temp.add(t.val);
                if(t.left != null){
                    tempQ.offer(t.left);
                }
                if(t.right != null){
                    tempQ.offer(t.right);
                }
            }
            result.add(temp);
            q = tempQ;
        }
        return result;
    }
}