题解 | #凯撒密码#

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

string decode(string str, int d) {
    // write code here
    string res = "";
    vector<char> charVec;
    for (int i = 48; i <= 57; i++) {
        charVec.push_back(char(i));
    }

    for (int i = 65; i <= 90; i++) {
        charVec.push_back(char(i));
    }

    for (int i = 97; i <= 122; i++) {
        charVec.push_back(char(i));
    }
    for (int i = 0; i < str.size(); i++) {
        if (str[i] <= '9'&&str[i] >= '0') {
            int num = str[i] - 48 - d;
            if (num < 0) {
                num = charVec.size() + num;
            }
            res += charVec[num];
        }
        else if (str[i] >= 'A'&&str[i] <= 'Z') {
            int num = str[i] - 65+10 - d;
            if (num < 0) {
                num = charVec.size() + num;
            }
            res += charVec[num];
        }else if (str[i] >= 'a'&&str[i] <= 'z') {
            int num = str[i] - 97+10+26 - d;
            if (num < 0) {
                num = charVec.size() + num;
            }
            res += charVec[num];
        }
    }
    return res;
}

int main() {
    string res = decode("pqyeqfgt", 2);
    cout << res << endl;
}