C++ Math

# C++: Count in Factors

Write a program which counts up from 1, displaying each number as the multiplication of its prime factors. For the purpose of this task, 1 may be shown as itself.

For examle, 2 is prime, so it would be shown as itself. 6 is not prime; it would be shown as $2\times3$. Likewise, 2144 is not prime; it would be shown as $2\times2\times2\times2\times2\times67$.

#include <iostream>
#include <sstream>
#include <iomanip>
using namespace std;

void getPrimeFactors( int li )
{
int f = 2; string res;
if( li == 1 ) res = "1";
else
{
while( true )
{
if( !( li % f ) )
{
stringstream ss; ss << f;
res += ss.str();
li /= f; if( li == 1 ) break;
res += " x ";
}
else f++;
}
}
cout << res << "\n";
}

int main( int argc, char* argv[] )
{
for( int x = 1; x < 101; x++ )
{
cout << right << setw( 4 ) << x << ": ";
getPrimeFactors( x );
}
cout << 2144 << ": "; getPrimeFactors( 2144 );
cout << "\n\n";
return system( "pause" );
}

Output:
   1: 1
2: 2
3: 3
4: 2 x 2
5: 5
6: 2 x 3
7: 7
8: 2 x 2 x 2
9: 3 x 3
10: 2 x 5
11: 11
12: 2 x 2 x 3
13: 13
14: 2 x 7
15: 3 x 5
16: 2 x 2 x 2 x 2
17: 17
18: 2 x 3 x 3
19: 19
20: 2 x 2 x 5
21: 3 x 7
22: 2 x 11
23: 23
24: 2 x 2 x 2 x 3
.
.
.

SOURCE

Content is available under GNU Free Documentation License 1.2.