C++ 詳解
DFS + 記憶化搜尋
https://www.tseng-school.com/2026/02/11/apcs/apcs202511/#%E7%AC%AC%E4%B8%80%E9%A1%8C-%E5%AD%97%E6%AF%8D%E9%85%8D%E5%B0%8D-ZeroJudge-r626