Pythonで LeftStrRightStr Substringなどの処理はsliceのみです。 ↑のコードは、2文字目〜3文字目を取得できます s2 = 「いう」です。

The key idea is to use a sliding window approach with two pointers. Maintain a window (substring) using two pointers, and a set to track characters within the current window. Move the right pointer to ...