华为机试：简单密码

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

char c_to_n(char ch) {
    ch = (ch >= 'a' && ch <= 'c') ? '2' : ch;
    ch = (ch >= 'd' && ch <= 'f') ? '3' : ch;
    ch = (ch >= 'g' && ch <= 'i') ? '4' : ch;
    ch = (ch >= 'j' && ch <= 'l') ? '5' : ch;
    ch = (ch >= 'm' && ch <= 'o') ? '6' : ch;
    ch = (ch >= 'p' && ch <= 's') ? '7' : ch;
    ch = (ch >= 't' && ch <= 'v') ? '8' : ch;
    ch = (ch >= 'w' && ch <= 'z') ? '9' : ch;
    return ch;
}

int main() {
    // int a, b;
    // while (cin >> a >> b) { // 注意 while 处理多个 case
    //     cout << a + b << endl;
    // }
    char ch;
    string ans;
    while (cin >> ch) {
        if (ch >= 'a' && ch <= 'z') {
            ans.push_back(c_to_n(ch));
        } else if (ch >= 'A' && ch <= 'Z') {
            ch = tolower(ch);
            if (ch + 1 > 'z') {
                ch = 'a';
            } else {
                ch += 1;
            }
            ans.push_back(ch);
        }
        else {
            ans.push_back(ch);
        }
    }
    cout << ans << endl;
    return 0;
}