题解 | #字符串加解密#

#include <iostream>
using namespace std;
#include <cctype>
string encrypt(string a) {
    string b = a;
    int num;
    char l;
    for (int i = 0; i < a.size(); i++) {
        if (isdigit(a[i])) {
            num = a[i] - '0';
            if (num <= 8) {
                num++;
            } else if (num == 9) {
                num = 0;
            }

            b[i] = num + '0';
        } else if (islower(a[i])) {
            if (a[i] != 'z') {
                b[i] = toupper((a[i] + 1));
            } else {
                b[i] = 'A';
            }
        } else if (isupper(a[i])) {
            if (a[i] != 'Z') {
                b[i] = tolower((a[i] + 1));
            } else {
                b[i] = 'a';
            }
        } else {
            b[i] = a[i];
        }
    }
    return b;
}

string decrypt(string a) {
    string b = a;
    int num;
    char l;
    for (int i = 0; i < a.size(); i++) {
        if (isdigit(a[i])) {
            num = a[i] - '0';
            if (num > 0) {
                num--;
            } else if (num == 0) {
                num = 9;
            }

            b[i] = num + '0';
        } else if (islower(a[i])) {
            if (a[i] != 'a') {
                b[i] = toupper((a[i] - 1));
            } else {
                b[i] = 'Z';
            }
        } else if (isupper(a[i])) {
            if (a[i] != 'A') {
                b[i] = tolower((a[i] - 1));
            } else {
                b[i] = 'z';
            }
        } else {
            b[i] = a[i];
        }
    }
    return b;
}

int main() {
    string a;
    string b;
    cin >> a;
    cout << encrypt(a) << endl;
    cin >> b;
    cout << decrypt(b) << endl;
}

cctype的使用