字符调整
/** 大小写转换、获取字母序
- 2024-03-16: https://qoj.ac/submission/355156
 **/
 void rev(std::string &s) {
 int l = s.size();
 for (int i = 1; i < l; i += 2) {
 if (std::isupper(s[i])) {
 s[i] = std::tolower(s[i]);
 } else {
 s[i] = std::toupper(s[i]);
 }
 }
 }
int get(char c) {
int x;
if (std::islower(c)) {
x = c - 'a';
} else {
x = 26 + c - 'A';
}
return x;
}
