CODEWITHSUNDEEP
c++c++11
TDeV4
TDeV4

Reputation: 11

Unable to print statement C++

I am trying to create the binary representation of a given integer, however, when I try to output the string, binaryNum, at the end of the code, nothing is printed. However, if I run cout within the for loop, it will print out the binary representation as the program adds 0's and 1's (I only want the final output, not the steps along the way).

What am I missing?

#include <string>
#include <iostream>
using namespace std;

int main() {
    int num;
    string binaryNum = "";
    int divisor = 1;

    cin >> num;

    while (num > 0) {
        while (num / divisor > 1) {
            divisor *= 2;
        }
        if (num / divisor == 1) {
            binaryNum.push_back('1');
            num = num - divisor;
            divisor /= 2;
            while (num / divisor < 1) {
                divisor /= 2;
                binaryNum.push_back('0');
            }
        }
    }

    cout << binaryNum << endl;

    return 0;
}

Thanks!

Upvotes: 0

Views: 89

Answers (3)

Darth-CodeX
Darth-CodeX

Reputation: 2662

Use bitset header file of C++11 to ease your workflow. For an example:

#include <bitset>
#include <string>
#include <iostream>
#include <limits>

int main(void)
{
    int my_num = 0;
    std::cout << "Enter a number: ";
    std::cin >> my_num;
    std::bitset<std::numeric_limits<int>::digits> foo(my_num);
    std::cout << my_num << " in binary = " << foo << std::endl;
    return 0;
}

Further Reading:

Upvotes: 1

The Coding Fox
The Coding Fox

Reputation: 1585

You can use bitset to convert decimal to binary as such:

#include <string>
#include <iostream>
#include <bitset>

int main() 
{
    unsigned int num;
    std::cin >> num;

    std::cout << std::bitset<8>{num} << std::endl; // Replace 8 with the number of binary digits you wish to print.

    return 0;
}

But the catch here is that this way, the binary number is limited to 8 digits (in this case). So let's talk about your code.

The problem with your code is that at one point, the divisor's value turns to 0. Now you are then doing the following:

while (num / divisor < 1)

And we all know, division by 0 is not possible. So to fix your error, add the following line after 'divisor /= 0;':

if (divisor == 0) break;

This will break out of the major while loop 'while (num > 0)' if divisor == 0, and then will print binaryNum.

Final code:

#include <string>
#include <iostream>

int main() {
    int num;
    std::string binaryNum = "";
    int divisor = 1;

    std::cin >> num;

    while (num > 0) {
        while (num / divisor > 1) {
            divisor *= 2;
        }
        if (num / divisor == 1) {
            binaryNum.push_back('1');
            num = num - divisor;
            divisor /= 2;

            if (divisor == 0) break;
            while (num / divisor < 1) {
                divisor /= 2;
                binaryNum.push_back('0');
            }
        }
    }

    std::cout << binaryNum << std::endl;

    return 0;
}

Also, consider not using the following line in your code:

using namespace std;

...as it is considered as bed practice.

Upvotes: 0

Drew Dormann
Drew Dormann

Reputation: 63704

What am I missing?

You are dividing by zero, causing Undefined Behavior.

Consider when num and divisor are 1.

    while (num / divisor > 1) {
        divisor *= 2;
    }

The code above will not loop. 1 > 1 is not true.

    if (num / divisor == 1) {

Then the above if is entered, because 1 == 1.

        binaryNum.push_back('1');
        num = num - divisor;
        divisor /= 2;
        while (num / divisor < 1) {

Then the above code makes divisor equal to 0.

Your algorithm then divides by zero,

Upvotes: 3

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