102. 二叉树的层序遍历 https://leetcode.cn/problems/binary-tree-level-order-traversal
107. 二叉树的层序遍历 II https://leetcode.cn/problems/binary-tree-level-order-traversal-ii
103. 二叉树的锯齿形层序遍历 https://leetcode.cn/problems/binary-tree-zigzag-level-order-traversal
117. 填充每个节点的下一个右侧节点指针 II https://leetcode.cn/problems/populating-next-right-pointers-in-each-node-ii
662. 二叉树最大宽度 https://leetcode.cn/problems/maximum-width-of-binary-tree
515. 在每个树行中找最大值 https://leetcode.cn/problems/find-largest-value-in-each-tree-row
637. 二叉树的层平均值 https://leetcode.cn/problems/average-of-levels-in-binary-tree
958. 二叉树的完全性检验 https://leetcode.cn/problems/check-completeness-of-a-binary-tree
1161. 最大层内元素和 https://leetcode.cn/problems/maximum-level-sum-of-a-binary-tree
1302. 层数最深叶子节点的和 https://leetcode.cn/problems/deepest-leaves-sum
1609. 奇偶树 https://leetcode.cn/problems/even-odd-tree
二叉树大部分题目都可以用递归的算法解决，但少部分题目用递归比较麻烦的话，我们可以考虑使用层序遍历的方式解决。