From decimal to hexa. haloa guys, i've a problem on a code in c++.

[alibierto]

Hi, i'm new on this forum.
I have to make a program that transform a decimal number to hexadecimal. The code works only for some decimal values. Like 4095, 3058, 405, 1315 ..... but it does not work for many other values ​​like: 3586, 3584 ...
I do not know which saint to pray so I thought I'd ask you to help.
thanks for any suggestions and help.

#include <iostream>

using namespace std;

int main()
{ int a,c;

cin>>a;
c=144;
while (c>16)
{
if (a>16 && a<256)
{

c=a%16;
a=a/16;
switch (a)
{
case 10:
cout<<"A";
break;
case 11:
cout<<"B";
break;
case 12:
cout<<"C";
break;
case 13:
cout<<"D";
break;
case 14:
cout<<"E";
break;
case 15:
cout<<"F";
break;
default:
cout<<a;
break;

}
switch (c)
{
case 10:
cout<<"A";
break;
case 11:
cout<<"B";
break;
case 12:
cout<<"C";
break;
case 13:
cout<<"D";
break;
case 14:
cout<<"E";
break;
case 15:
cout<<"F";
break;
default:
cout<<c;
break;
}
}
if (a>256 && a<4096)
{
c=a%256;

a=a/256;

switch (a)
{
case 10:
cout<<"A";
break;
case 11:
cout<<"B";
break;
case 12:
cout<<"C";
break;
case 13:
cout<<"D";
break;
case 14:
cout<<"E";
break;
case 15:
cout<<"F";
break;
default:
cout<<a;
break;

}



}

if (a>4096)
{
c=a%4096;

a=a/4096;

switch (a)
{
case 10:
cout<<"A";
break;
case 11:
cout<<"B";
break;
case 12:
cout<<"C";
break;
case 13:
cout<<"D";
break;
case 14:
cout<<"E";
break;
case 15:
cout<<"F";
break;
default:
cout<<a;
break;

}
}
a=c;
}


cout<<endl;


system("PAUSE");
return 0;
}


P.S.
(where are the smile in this forum?)

[MiiNiPaa]

It is easier to rewrite that code from scratch than to fing logic error in it.
For example:

#include <array>
#include <iostream>
#include <string>


std::string to_hex(unsigned number)
{
    static const std::array<char, 16> hexdigits =
        {'0', '1', '2', '3', '4', '5', '6', '7',
         '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',};
    std::string hex;
    while (number != 0) {
        hex.push_back(hexdigits[number % 16]);
        number /= 16;
    }
    return {hex.rbegin(), hex.rend()};
}


int main()
{
    unsigned number;
    std::cin >> number;
    std::cout << to_hex(number) << std::endl;
}

http://ideone.com/uEb3O4

[alibierto]

Minipaa, I've to do an exercise that transform decimal to hexadecimal whiteout shortcuts, the challenge is this. Can you help me, and analyze the code for find the error. Thank

[JLBorges]

#include <iostream>

void print_hex_digits( unsigned int n )
{
    static const unsigned int RADIX = 16 ;
    static const char hex_digits[] = "0123456789abcdef" ;

    char digit = hex_digits[ n % RADIX ] ;
    if( n >= RADIX ) print_hex_digits( n / RADIX ) ;
    std::cout << digit ;
}

void print_hex( unsigned int n )
{
    std::cout << "0x" ;
    print_hex_digits(n) ;
    std::cout << '\n' ;
}


int main()
{
    unsigned int numbers[] = { 0, 4095, 3058, 405, 1315, 3586, 3584, 12345678, 2882400018 } ; 
    for( unsigned int n : numbers ) print_hex(n) ;
}

http://coliru.stacked-crooked.com/a/b0731ab4cd5eef35