C++: Binary to Decimal w/ Appearance of the Conversion Process

Question

Im trying to make a program that converts binary to decimal but having the needs to show the process of the convertion

Enter a binary number: 10110

1*(2^4) + 1*(2^2) + 1*(2^1)

the decimal equivalent of 10110 is: 22

but instead the value of the counter in the middle of the loop fails to decrease, leading to this

SAMPLE IMAGE

this is my current code

#include <iostream>
#include <math.h>
#include <string>

using namespace std;

int main()
{
     int bin, dec = 0, remainder, num, base = 1,counter=0,counter2=0, constnum;
     cout << "Enter the binary number: ";
     cin >> num;
     bin = num;
     constnum = num;
     while(bin > 0)
     {
        bin=bin/10;
        counter2++;
     }

     while (num > 0)
     {
        if (num % 10 == 1) {
            cout << " 1*(2^" << counter2 << ") +";
            counter2--; 
            }
         else if(num % 10 == 0) {
            counter2--;
         }
         remainder = num % 10; //get the last digit of the input
         dec = dec + remainder * base;
         base = base * 2;
         num = num / 10;

    }

     cout << "\nThe decimal equivalent of " << constnum << " : " << dec << endl;
     return 0;

}

Answer 1

As already pointed out, you are calculating and displaying the result in different orders. I suggest that you store the result and display it later. Something like:

#include <sstream>
....

int pos = 0;
string res;
while (num > 0) {
    if (num % 10 == 1) {
        stringstream out;
        out << "1*(2^" << pos << ") + ";

        res = out.str() + res;
    }

    remainder = num % 10; //get the last digit of the input
    dec = dec + remainder * base;
    base = base * 2;
    num = num / 10;
    pos++;
}

int len = res.length();
// to remove the last '+'
if (len >= 3) {
    res = res.substr(0, len - 3);
}

cout << res;

Answer 2

you should wirte the process in ascendant order, instead of descendant, this is to match your algorithim, which is in ascendant order

So, in your last while, instead of this:

if (num % 10 == 1) {
        cout << " 1*(2^" << counter2 << ") +";
        counter2--; 
        }
else if(num % 10 == 0) {
        counter2--;
     }

you should do this:

if (num % 10 == 1) {
        cout << " 1*(2^" << counter << ") +";
        counter++;
    }
else if(num % 10 == 0) {
        counter++;
    }

also, if you follow my recommendation, you may erase your first while:

while(bin > 0)
 {
    bin=bin/10;
    counter2++;
 }

because is no longer needed

Answer 3

Just use a bit set:

#include <bitset>
#include <iostream>

int main()
{
    std::bitset<32> val;
    std::cin >> val;
    std::cout << val.to_ulong() << "\n";
}