CODEWITHSUNDEEP
c++
carlosp120
carlosp120

Reputation: 76

Decimal to Binary Signed in C++

This is what I have:

string decimal_to_binary(int n){
string result = "";
while(n > 0){
    result = string(1, (char) (n%2 + 48)) + result;
    n = n/2;
}
return result; }

This works, but it doesn't work if I put a negative number, any help?

Upvotes: 4

Views: 4600

Answers (3)

doedotdev
doedotdev

Reputation: 575

Well I would recommend calling a separate function for negative numbers. Given that, for example, -1 and 255 will both return 11111111. Converting from the positive to the negative would be easiest instead of changing the logic entirely to handle both.

Going from the positive binary to the negative is just running XOR and adding 1.

You can modify your code like this for a quick fix.

string decimal_to_binary(int n){
    if (n<0){ // check if negative and alter the number
        n = 256 + n;
    }
    string result = "";
    while(n > 0){
        result = string(1, (char) (n%2 + 48)) + result;
        n = n/2;
    }
    return result;
}

Upvotes: 1

R Sahu
R Sahu

Reputation: 206607

This works, but it doesn't work if I put a negative number, any help?

Check whether the number is negative. If so, call the function again with -n and return the concatenated result.

You also need to add a clause to check against 0 unless you want to return an empty string when the input is 0.

std::string decimal_to_binary(int n){
   if ( n < 0 )
   {
      return std::string("-") + decimal_to_binary(-n);
   }

   if ( n == 0 )
   {
      return std::string("0");
   }

   std::string result = "";
   while(n > 0){
      result = std::string(1, (char) (n%2 + 48)) + result;
      n = n/2;
   }
   return result;
}

Upvotes: 0

Sam Mokari
Sam Mokari

Reputation: 471

Just

#include <bitset>

Then use bitset and to_string to convert from int to string

std::cout << std::bitset<sizeof(n)*8>(n).to_string();

It works for negative numbers too.

Upvotes: 2

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