pc2017C

#include <iostream>
#include <string>
#include <string.h>

#include <vector>

#define print(var) ;//cout << #var << ": " << var<< endl;

using namespace std;

string decode(string inp, int base);
string code(string inp, int base);

void reverseString(string* str) {
    int length = str->length();
    for (int i = 0; i < (length / 2); i++) {
        char tmp = str->at(i);
        str->at(i) = str->at(length - 1 - i);
        str->at(length - 1 - i) = tmp;
    }
}


int main() {
    int tests;
    cin >> tests;
    cin.ignore();


    while (tests--) {
        int base;
        int op;
        string inp;
        getline(cin, inp);
        base = (inp.at(0) - '0');
        op = (inp.at(2) - '0');
        inp.erase(0, 4);
        print(base);
        print(op);
        print(inp);

        if (op) {
            cout << decode(inp, base) << ":\n";
        }
        else {
            cout << code(inp, base) << ":\n";
        }
    }
}

string decode(string inp, int base) {
    int toBase = inp.length() % base;

    if (toBase) {
        for (int i = 0; i < base - toBase; i++) {
            inp += " ";
        }
    }
    int loops = inp.length() / base;

    string dcode;
    string result;

    for (int i = 0; i < loops; i++) {
        dcode = inp.substr(0, base);
        inp.erase(0, base);
        reverseString(&dcode);
        result += dcode;
    }

    while (result.find_last_of(' ') == result.length() - 1) {
        result.erase(result.find_last_of(' '));
    }
    return result;
}


string code(string inp, int base) {
    int toBase = inp.length() % base;

    if (toBase) {
        for (int i = 0; i < base - toBase; i++) {
            inp += " ";
        }
    }

    int loops = inp.length() / base;

    string code;
    string result;

    for (int i = 0; i < loops; i++) {
        code = inp.substr(0, base);
        inp.erase(0, base);
        reverseString(&code);
        result += code;
    }

    return result;
}

/*
5
5 0 abcdefghijklmnopqrstuvwxyz
5 1 edcbajihgfonmlktsrqpyxwvu    z
2 0 jereme
2 1 ejerem
5 1 a

2
5 1 edcbajihgfonmlktsrqpyxwvu    z
2 1 ejerem
*/