对于这种会变成环状的,一般可以考虑取模
#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
string a;
getline(cin, a);
for (int i = 0; i < a.size(); ++i)
{
if (a[i] >= 'A' && a[i] <= 'Z') //是大写字母
a[i] = (a[i] - 'A' + 1) % 26 + 'A';
else if (a[i] >= 'a' && a[i] <= 'z')
a[i] = (a[i] - 'a' + 1) % 26 + 'a';
}
cout << a << endl;
return 0;
}