i need to convert decimal to twos complement binary and then add the binary digits but...

i need to convert decimal to twos complement binary and then add the binary digits but I am unable to do it. I am only allowed to use string, can anyone help me out please. i need the code urgently.

#include
#include
#include
#include

using namespace std;

string reverse(string s)
{
string x = "";
for (long i = s.length() - 1; i >= 0; i--)
{
x += s[i];
}
return x;
}
string twosComplementStringsAddition(string A, string B)
{
string c;
int count = 0;
for (int i = 0; i < A.length(); i++)
{
string c;
c.resize(A.length());
if (count > 0)
c[i] = '1';
else if (A[i] == '1' & B[i] == '1')
{
c[i] = '0';
count++;
}
else if ((A[i] == '1' & B[i] == '0') || (A[i] == '0' & B[i] == '1'))
c[i] = '1';
else if (A[i] == '0' & B[i] == '0')
c[i] = '0';
count = 0;
}
return c;
}
string negative(string a)
{
for (int i = 0; i < a.length(); i++)
{
if (a[i] == '1')
a[i] = '0';
else
a[i] = '1';
}
reverse(a);
string x = "1";
twosComplementStringsAddition(a, x);
reverse(a);
return a;
}
string decimalToTwosComplementString(int a, int L)
{
{

for (int i = L - 1; i >= 0; i--)
{
int k = a >> i;
if (k & 1)
cout << "1";
else
cout << "0";
}
}
string s = " ";
L = s.length();
int b;
for (int i = 0; i < L - 1; i++)
{
b = a % 2;
if (b == 1)
s[i] = '1';
else if (b == 0)
s[i] = '0';
a = a / 2;
}
reverse(s);
if (a < 0)
{
negative(s);
return s;
}
else
return s;
}
int twosComplementStringToDecimal(string a)
{
int result = 0;
if (a[0] == '0')
{
reverse(a);
for (int i = 0; i < a.length(); i++)
{
if (a[i] == '1')
{
result = result + pow(2, static_cast(i));
}
else if (a[i] == '0')
{
result = result + 0;
}
}
}
else
{
negative(a);
int resulta = 0;
reverse(a);
for (int i = 0; i < a.length(); i++)
{
if (a[i] == '1')
{
resulta = resulta + pow(2, static_cast(i));
}
else if (a[i] == '0')
{
resulta = resulta + 0;
}
}
return resulta;
}
return result;
}
int main()
{
   //Read in the bit pattern size
   int L;
   do
   {
       cout << "Enter positive integer for the bit pattern size ";
       cin >> L;
   } while (L <= 0);

   //Read in two integers a and b
   int a, b;
   cout << "Enter an integer a ";
   cin >> a;
   cout << "Enter an integer b ";
   cin >> b;

   //Calculate the decimal arithmetic sum of a and b and print the result
   int c1 = a + b;
   cout << "In decimal " << a << " + " << b << " is " << c1 << endl;

   //Compute the two's complement representations of a and b
   //Each integer must be represented in L-bits pattern
   //Also these two's complement representations must be returned as string data types
   string A = decimalToTwosComplementString(a, L);
   string B = decimalToTwosComplementString(b, L);

   //Print the two's complement representations of a and b
   cout << "The two's complement of " << a << " is\t " << A << endl;
   cout << "The two's complement of " << b << " is\t " << B << endl;

   //Compute the binary sum of the two's complement representations of a and b
   //The result must be returned as L-bit pattern string data type
   string C = twosComplementStringsAddition(A, B);

//Print the two's complement representation binary sum
cout << "The binary sum of " << A << " and " << B << " is " << C << endl;

   //Convert the two's complement representation binary sum to decimal and print
   int c2 = twosComplementStringToDecimal(C);
   cout << "In two's complement arithmetic, " << a << " + " << b << " is " << c2 << endl;

   //Print some concluding results
   if (c1 == c2)
       cout << c1 << " is equal to " << c2 << ". Good Job!" << endl;
   else
   {
       cout << c1 << " is not equal to " << c2 << endl;
       cout << "Either " << c1 << " cannot be represented by the given bit pattern OR we have made a mistake!" << endl;
   }
   system("Pause");
   return 0;
}

Expert Solution

Working code implemented in C++ and appropriate comments provided for better understanding.

Source Code:

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

//Helper function:convert the original decimal number to unsigned binary number.
string decimalToUnsign(int a, int L)
{
   string result = "";
   int r;
   while (a>0)
   {
       r = a%2;
       if(r == 1)
           result = "1" + result;
       else
           result = "0" + result;
       a /= 2;
   }
   int n = result.length();

   if (L >= n) {
       for(int i=0; i<L-n; i++)
           result = "0" + result;

   }
   else
   {
       string temp ="";
       for(int j = n-L; j < n; j++)
           temp += result[j];
       result = temp;
   }

return result;
}

//Function 1
string decimalToTwosComplementString(int a, int L)
{
   string result = "";

   if (a >= 0) {
       result = decimalToUnsign(a, L);
   }
   else
   {
       a = a * -1;
       result = decimalToUnsign(a, L);
       //flip
       string temp ="";
       for(int k=0; k<L; k++)
       {

           if (result[k]=='0')
               temp += "1";
           else
               temp += "0";
       }
       result = temp;
       //add 1
       string temp1 = "";
       for(int i = L-1; i>=0; i--)
       {
           if (result[i] == '0')
           {
               temp1 = "1" + temp1;
               break;
           } else {

               temp1 += "0";
           }
       }
       int size = temp1.length();
       for(int i=L-size-1; i>=0; i--)
       {
           temp1 = result[i] + temp1;
       }
       result = temp1;
   }
   return result;
}

//Function 2
int twosComplementStringToDecimal(string C)
{
   int num = 0;

   if (C[0] == '0')
   {
       int index = 0;
       for(int i= C.length()-1; i>=0; i--)
       {
           if(C[C.length()-1] == '1' && i == C.length()-1)
               num = 1;

           else if(C[i] == '1')
           {
               int temp = 1;
               for(int j = 0; j<index; j++)
                   temp *= 2;
               num += temp;
           }
           index++;
       }
   }
   else
   {
       string st ="";
       for(int k=0; k < C.length(); k++)
       {
           if (C[k]=='0')
               st += "1";
           else
               st += "0";
       }

       C = st;

       //add 1
       string temp1 = "";
       for(int i = C.length()-1; i>=0; i--)
       {
           if (C[i] == '0')
           {
               temp1 = "1" + temp1;
               break;
           }
           else
           {
               temp1 += "0";
           }
       }
       int size = temp1.length();
       for(int i=C.length()-size-1; i>=0; i--)
       {
           temp1 = C[i] + temp1;
       }

C = temp1;

       int index = 0;
       for(int i= C.length()-1; i>=0; i--)
       {
           if(C[C.length()-1] == '1' && i == C.length()-1)
               num = 1;

           else if(C[i] == '1')
           {
               int temp = 1;
               for(int j = 0; j<index; j++)
                   temp *= 2;
               num += temp;
           }
           index++;
       }
       num*= -1;
   }
   return num;
}

//Function 3
string twosComplementStringsAddition(string A, string B)
{
return decimalToTwosComplementString(twosComplementStringToDecimal(A) + twosComplementStringToDecimal(B), A.length());
}

//Main function code provided by Mr.Koopa :)
int main()
{
   //Read in the bit pattern size
   int L;
   do
   {
       cout << "Enter positive integer for the bit pattern size ";
       cin >> L;
   }while (L <= 0);