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tux4life

May 24th, 2009 1:16 pm

binary to decimal convertor

This snippet allows you to convert a text representation(*) of a binary number to a decimal number :)

(*): With 'text representation' I mean for example a string containing "1001" or "10001110011", etc. ...

#include <iostream>
#include <string>
 
using namespace std;
 
unsigned int pow(unsigned int a, unsigned int n);
 
int main()
{
    string binary;
    unsigned int decimal = 0;
 
    cout << "Enter a binary number: ";
    cin >> binary;
 
    for(int i = binary.length()-1; i >= 0; i--) {
        if(binary[i] > '1' || binary[i] < '0') {
            cout << "Invalid binary number!" << endl;
            return 1;
        } else {
            decimal += (binary[i] - '0') * pow(2, (binary.length()-i-1));
        }
    }
 
    cout << "Decimal: " << decimal << endl;	
    return 0;
}
 
unsigned int pow(unsigned int a, unsigned int n)
{
    unsigned int r = 1;
    while( n-- > 0 ) r *= a;
    return r;
}

amrith92

May 24th, 2009 3:24 pm

Nice code! But maybe the function name

pow

should be changed, to avoid any ambiguity caused if anybody chooses to include

<cmath>

with that :) ...

tux4life

May 24th, 2009 4:48 pm

Yep, there you've got a point!
For those who are using the

cmath

library:
Change the name of the

pow

function to apow/mypow/pow2 or whatever you like :P

William Hemsworth

May 25th, 2009 12:00 pm

Here's how I would have done it:

#include <iostream>

using namespace std;



int main() {

  char binary[33]; // 32bit + '\0'

  unsigned int decimal = 0;



  cout << "Enter binary:\n> ";



  cin.getline( binary, 32 );

  unsigned int exp = 1;



  for (int i = (int)strlen( binary ) - 1; i >= 0; --i) {

    if ( binary[i] == '1' )

      decimal += exp;



    exp <<= 1;

  }



  cout << "\nDecimal:\n> " << decimal;



  cin.ignore();

}

tux4life

May 25th, 2009 12:48 pm

I'm glad to know that there was actually no need for a separate function like pow, the bit shifting is a superior method to multiplicate it every time by two!
And William, your program will threat any other value than '1' as a '0', this isn't wrong IMO, but I only wanted to let you know in case you didn't (but probably you did know this already, because you're always one step ahead :))
I learned again from your code, you're superior in writing efficient and very easy to understand code :) !!

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