Codeforces - 1B

#define _CRT_SECURE_NO_WARNINGS
#include <cstdio> // cstdio is faster, right? I don't know if I should mix it with iostream
#include <cctype>
#include <algorithm>
#include <iostream>
#include <string>

std::string charToNum(const std::string cell);
std::string numToChar(const std::string cell);
std::string convert(const std::string cell);
unsigned uPow(unsigned base, unsigned exponent);

int main() {
    unsigned n;
    std::scanf("%u", &n);
    std::getchar();

    std::string input;
    for (unsigned i = 0; i < n; ++i) {
        std::getline(std::cin, input);

        std::printf("%s\n", convert(input).c_str());
    }
}

std::string charToNum(const std::string cell) {
    std::string columnsStr;

    // we'll proccess letters to a number later, first we need to extract columns and rows
    unsigned i = 0; // we'll need that after the loop
    while (std::isalpha(cell[i])) // string "cell" for sure ends with a number, so we're not gonna go past it
        columnsStr += cell[i++];

    unsigned rows, columns = 0;
    std::sscanf(cell.c_str() + i, "%u", &rows);

    //convert columns from letters to the number
    for (size_t i = 0, j = columnsStr.size(); i < columnsStr.size(); ++i, --j)
        columns += uPow(26, j - 1) * (columnsStr[i] - 'A' + 1);

    return {'R' + std::to_string(rows) + 'C' + std::to_string(columns)};
}

std::string numToChar(const std::string cell) {
    unsigned rows, columns;
    std::sscanf(cell.c_str(), "R%uC%u", &rows, &columns);

    // convert columns from the number to letters
    std::string columnsStr;
    for (size_t i = columns; i; i = (i - 1) / 26)
        columnsStr += (i % 26 != 0) ? 'A' + i % 26 - 1 : 'Z'; // if 26 | i we have a Z

    // letters are readen ltr, text is rtl
    std::reverse(columnsStr.begin(), columnsStr.end());

    return {columnsStr + std::to_string(rows)};
}

std::string convert(const std::string cell) {
    bool lettersTwice = true; // set it to true, so that first letter in string doesn't trigger if statement

    // if last char isn't a letter and this one is, we've got letters twice
    for (unsigned i = 0; i < cell.size(); ++i)
        if (!lettersTwice && std::isalpha(cell[i])) {
            lettersTwice = true;
            break;
        }
        else
            lettersTwice = std::isalpha(cell[i]);

    if (lettersTwice)
        return numToChar(cell);
    else
        return charToNum(cell);
}

unsigned uPow(unsigned base, unsigned exponent) {
    unsigned ret = 1;
    for (unsigned i = 0; i < exponent; ++i)
        ret *= base;
    return ret;
}