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;
}``````
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Last Post by mvmalderen

Nice code! But maybe the function name `pow` should be changed, to avoid any ambiguity caused if anybody chooses to include `<cmath>` with that :) ...

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

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();
}``````

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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