涉及知识点：字符串处理。解题思路记录每个字符出现的第$1$个位置和最后$1$个位置，询问时比较大小即可。代码#include<bits/stdc++.h>//#defineintlonglong#definell__int128#definedbdouble#defineldblongdouble#definevovoid#defineendl'\n'#defin