Comma Formatting for numbers in C++ - c++

Question

I'm needing help in adding commas to the number the user enters, some guidance or help would be appreciated. So far I have it where i store the first three digits and the last six digits and then simply format it.
#include<iostream>
using namespace std;
int main ( int argc, char * argv[] )
{
unsigned long long userInput;
int fthreeDigit;
cout << "Enter a long long number: " << endl;
cin >> userInput;
fthreeDigit = ( userInput / 1000 );
userInput %= 1000;
cout << "Your Number: " << fthreeDigit << "," << userInput << endl;
system("pause");
return 0;
}

Answer 1

Is this what you need? The locale will do this for you correctly.
#include <iostream>
using namespace std;
int main ( int argc, char * argv[] )
{
unsigned long long userInput;
int fthreeDigit;
cout << "Enter a long long number: " << endl;
cin >> userInput;
std::cout.imbue(std::locale(""));
std::cout << userInput << std::endl;
return 0;
}

Answer 2

EDIT:
I have two solutions. first without playing with numbers (recommended) and second (division).
first solution is:
#include <cstdlib>
#include <iostream>
#include <locale>
#include <string>
using namespace std;
struct my_facet : public std::numpunct<char>{
explicit my_facet(size_t refs = 0) : std::numpunct<char>(refs) {}
virtual char do_thousands_sep() const { return ','; }
virtual std::string do_grouping() const { return "\003"; }
};
/*
*
*/
int main(int argc, char** argv) {
cout<<"before. number 5000000: "<<5000000<<endl;
std::locale global;
std::locale withgroupings(global, new my_facet);
std::locale was = std::cout.imbue(withgroupings);
cout<<"after. number 5000000: "<<5000000<<endl;
std::cout.imbue(was);
cout<<"and again as before. number 5000000: "<<5000000<<endl;
return 0;
}
before. number 5000000: 5000000
after. number 5000000: 5,000,000
and again as before. number 5000000: 5000000
RUN SUCCESSFUL (total time: 54ms)
and second (not recommended) is :
double f = 23.43;
std::string f_str = std::to_string(f);
or this
int a = 1;
stringstream ss;
ss << a;
string str = ss.str();
Then you can use string::substr() string::find() string::find_first_of() and similar methods to modify and format your string.
a similar topic
If you really want (have to) divide: (I think my version is cleaner & more efficient than the others)
unsigned long long userInput;
std::stringstream ss,s0;
std::string nr;
std::cout << "Enter a long long number: " << std::endl;
std::cin >> userInput;
int input=userInput;
int digits;
while(input>999){
input=input/1000;
digits=userInput-input*1000;
int mdigits=digits;
while(mdigits<100){s0<<"0";mdigits*=10;}
std::string s=ss.str();
ss.str("");
ss<<","<<s0.str()<<digits<<s;
userInput=input;
s0.str("");
}
std::string sf=ss.str();
ss.str("");
ss<<input<<sf;
std::cout << "Your Number: " << userInput << ";" << digits <<";"<<ss.str()<<std::endl;
Enter a long long number: 12345678 Your Number: 12;345;12,345,678

Answer 3

Here is the brute force but may be easiest to understand way to get every thousand digits with the help of a vector.
#include<iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main ( int argc, char * argv[] )
{
long long userInput;
int fthreeDigit;
cout << "Enter a long long number: " << endl;
cin >> userInput;
vector <int> res; //use vector to store every 3 digits
while (userInput !=0)
{
fthreeDigit = userInput %1000;
res.push_back(fthreeDigit);
userInput = userInput / 1000 ;
}
std::reverse(res.begin(), res.end());
for (size_t i = 0; i < res.size()-1; ++i)
{
if (res[i] ==0)
{
cout << "000"<<",";
}
else
{
cout << res[i] << ",";
}
}
if (res[res.size()-1] == 0)
{
cout << "000";
}
else{
cout << res[res.size()-1];
}
cout <<endl;
cin.get();
return 0;
}
I tested this code with the following case:
Input: 123456 Output: 123,456
Input: 12 Output: 12
Input: 12345 Output: 12,345
Input: 1234567 Output: 1,234,567
Input: 123456789 Output: 123,456,789
Input: 12345678 Output: 12,345,678
I guess this is what you want according to your response to comments.

Answer 4

You could do this:
#include <iostream>
#include <string>
using namespace std;
string commify(unsigned long long n)
{
string s;
int cnt = 0;
do
{
s.insert(0, 1, char('0' + n % 10));
n /= 10;
if (++cnt == 3 && n)
{
s.insert(0, 1, ',');
cnt = 0;
}
} while (n);
return s;
}
int main()
{
cout << commify(0) << endl;
cout << commify(1) << endl;
cout << commify(999) << endl;
cout << commify(1000) << endl;
cout << commify(1000000) << endl;
cout << commify(1234567890ULL) << endl;
return 0;
}
Output (ideone):
0
1
999
1,000
1,000,000
1,234,567,890

Answer 5

// Accepts a long number, returns a comma formatted string
CString num_with_commas(long lnumber)
{
CString num;
num.Format(%d",lnumber);
if(num.GetLength() > 3) {num.Insert(num.GetLength()-3, ',');}
if(num.GetLength() > 7) { num.Insert(num.GetLength()-7, ','); }
if (num.GetLength() > 12) { num.Insert(num.GetLength()-12, ','); }
return(num);
}