题目链接

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题目描述

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。
与上题几乎一样

解题思路

public class Solution {
   
    public ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
   
        ArrayList<ArrayList<Integer>> res = new ArrayList<>();
        Queue<TreeNode> q = new LinkedList<>();
        q.add(pRoot);
        while (!q.isEmpty()) {
   
            ArrayList<Integer> row = new ArrayList<>();
            int cnt = q.size();
            while (cnt-- > 0) {
   
                TreeNode node = q.remove();
                if (node==null) continue;
                row.add(node.val);
                q.add(node.left);
                q.add(node.right);
            }
            if (row.size()>0) res.add(row);
        }
        return res;
    }
}

public class Solution {
   
    public ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
   
        ArrayList<ArrayList<Integer>> res = new ArrayList<>();
        ArrayList<Integer> row = new ArrayList<>();
        Queue<TreeNode> q = new LinkedList<>();
        q.add(pRoot);
        while (!q.isEmpty()) {
   
            int cnt = q.size();
            while (cnt-- > 0) {
   
                TreeNode node = q.remove();
                if (node==null) continue;
                row.add(node.val);
                q.add(node.left);
                q.add(node.right);
            }
            if (row.size()>0) {
   
                res.add(new ArrayList<>(row));
                row.clear();
            }
        }
        return res;
    }
}