HackerRank Encryption Problem https://www.hackerrank.com/challenges/encryption

hackerrank-encryption

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

string calc(string msg){

    int len,row,col,allot,margin;
    string str="";
    len=msg.length();
    row=floor(sqrt(len));
    col=ceil(sqrt(len));
    if(row*col<len)
        row++;
    margin=row*col-len;
    allot=row*col;
    
    for(int i=0;i<col;i++){
        
        for(int j=0;(i+j)<len;j+=col)
                 	str+=msg[i+j];
        
        str+=" ";
    }
    
    return str;
    
    
}

int main() {
    
    string msg;
    cin>>msg;
    cout<<calc(msg);
    
    return 0;
}