practice

1-B-spreadsheet.js

//http://codeforces.com/problemset/problem/1/B

var min = 64;

function convertNumToStr(num) {
    console.log(num)
    if(num <= 0) throw Error('Number must be greater than 0.');

    var result = 27;
    var remain;
    var str = '';

    if(num > 26) {
        while(result > 26) {
            result = Math.floor(num / 26);
            remain = num % 26;
            str += String.fromCharCode(result + min);
        }
        return str += String.fromCharCode(remain + min);
    } else {
        return String.fromCharCode(num + min);
    }
}

function convertStrToNum(str) {
    var n   = 0;
    var len = str.length;
    var base = 0;

    while(len--) {
        n += (+str[len].charCodeAt() - min) * Math.pow(26, base++);
    }
    return n;
}

function spreadsheets(n) {
    var rrxcy = /R(\d+)C(\d+)/i;
    var rcn   = /([a-z]+)(\d+)/i;
    var match;

    if(match = n.match(rrxcy)) {
        return convertNumToStr(match[2]) + match[1];
    } else {
        match = n.match(rcn);
        return match ? ('R' + match[2] + 'C' + convertStrToNum(match[1])) : 'Error!';
    }
}

//Test
console.log(spreadsheets('R23C55'));
console.log(spreadsheets('BC23'));