168. Excel表列名称/C++

string convertToTitle(int n) {
    string str;
    while(n){
        int m = n % 26;
        if(!m){
            m=26;
            n=n/26-1;
        }else            
            n /=26;
        char c = 'A' + m - 1;
        str = c + str;
    }
    return str;
}