“6250c44b6aaa593e04896fe3a396795d6a0cbf2e”上不存在“data_backup/1.leetcode/156-上下翻转二叉树/solution.json”
Do not use ctor * Reduce line of codes. * We can use virtual function for Maker now. * The implementation does not care what maker holds, it is easier to refactor later.