Addition of Array with different integer - c++

Question

Is there any way to add the sum of 2 binary numbers with this code ?
The end result I got when I add 12 and 24 is 010FF6F8(36). Which is different each time I add it up.
Everything works fine until the end when I wanted to add both of the binary numbers that I input into the sum of binary.
#include<iostream>
#include<cmath>
using namespace std;
int main()
{
int x1[10], x2[10], n1, n2, i, j, d1[10],d2[10];
int s1, s2;
cout << "\nEingabe Dezimalzahl 1 : ";
cin >> n1;
s1 = n1;
for (i = 0; n1 > 0; i++)
{
x1[i] = n1 % 2;
n1 = n1 / 2;
}
cout << "Dual : ";
for (i = i - 1; i >= 0; i--)
{
cout << x1[i];
d1[i] = x1[i];
}
cout << "\nEingabe Dezimalzahl 2 : ";
cin >> n2;
s2 = n2;
for (j = 0; n2 > 0; j++)
{
x2[j] = n2 % 2;
n2 = n2 / 2;
}
cout << "Dual : ";
for (j = j - 1; j >= 0; j--)
{
cout << x2[j];
d2[j] = x2[j];
}
cout << endl;
cout << "\nTest Addition und Zuweisung : \n";
cout << "-------------------------------\n";
int sumBin[10], sumDez;
int k = 0;
for (i = i - 1; i >= 0; i--)
{
for (j = j - 1; j >= 0; j--)
{
sumBin[k] = d1[i] + d2[j];
}
}
sumDez = s1 + s2;
cout << "zahl1 + zahl2 : " << sumBin << " (" << sumDez << ") \n";
}

Answer 1

I will paste now your source code with comments, where the errors are. I did this, while reading line by line. Without using a debugger.
I do strongly recommend that you do the same. Read line by line, and check what will happen.
Additionally. Please use a debugger. That will help you tremendously.
#include<iostream>
#include<cmath>
// Do not open the complete namespace
// Do not use this statement
using namespace std;
int main()
{
// You define a bunch of variables, which are not needed here
// Variables shall be defined, shortly before they are used
// And only in the scope, where they are elevant
// All variables shall be initialized. Always
// C-Style array shall be avoided, Used std::vector or std::array instead
// Magic numbers, like 10 shall be avoided. USe constexpr
int x1[10], x2[10], n1, n2, i, j, d1[10], d2[10];
int s1, s2;
cout << "\nEingabe Dezimalzahl 1 : ";
// Always check the result of an input operation. What if the user enters XXX
cin >> n1;
s1 = n1;
// This will work, but it is not the convential way for a for loop
for (i = 0; n1 > 0; i++)
{
x1[i] = n1 % 2;
n1 = n1 / 2;
}
// After this loop, i has a certain value
cout << "Dual : ";
// In this loop you decrement i
for (i = i - 1; i >= 0; i--)
{
cout << x1[i];
d1[i] = x1[i];
}
// And now, after this loop, i will be -1. Always
cout << "\nEingabe Dezimalzahl 2 : ";
cin >> n2;
s2 = n2;
// Same as above
for (j = 0; n2 > 0; j++)
{
x2[j] = n2 % 2;
n2 = n2 / 2;
}
cout << "Dual : ";
// Strange loop. Source of error. But will work here
for (j = j - 1; j >= 0; j--)
{
cout << x2[j];
d2[j] = x2[j];
}
// Now j is -1. Always
cout << endl;
cout << "\nTest Addition und Zuweisung : \n";
cout << "-------------------------------\n";
// Variable definition without initialization.
// Again. C-Style array and magic number
int sumBin[10], sumDez;
int k = 0;
// Remember from above? i is -1. Always.
// The following loop will never execute, becuase you set i to -2 in the beginning and then want to
// run the loop until i>=0. i is nver >= 0. The loop will not rund
for (i = i - 1; i >= 0; i--)
{
for (j = j - 1; j >= 0; j--)
{
sumBin[k] = d1[i] + d2[j];
}
}
sumDez = s1 + s2;
// std::cout cannot emit all avlues of the array. That you must do manually
cout << "zahl1 + zahl2 : " << sumBin << " (" << sumDez << ") \n";
}
Also you addition algorithm is not correct. You need to add bit by bit and include a carry over bit.
#include<iostream>
constexpr unsigned int MaxNumberOfBits = 128;
int main() {
// Inform user aout this program and what to do
std::cout << "\nSumming 2 number as binaries\n\nPlease enter 2 integer values:\n";
// Here we will store our 2 decimal numbers
unsigned int number1{};
unsigned int number2{};
// Read the 2 decimal numbers and check, if OK
if (std::cin >> number1 >> number2) {
// Ok, we read the 2 numbers. Now, we want to convert them to binary values
// Number 1. Resulting array to store value.
unsigned int binArray1[MaxNumberOfBits] = {};
// Bit index
unsigned int index1{};
// Process complete number 1
while ((number1 > 0) && (index1 < MaxNumberOfBits)) {
binArray1[index1] = number1 % 2;
number1 /= 2;
++index1;
}
// Number 2. Resulting array to store value.
unsigned int binArray2[MaxNumberOfBits] = {};
// Bit index
unsigned int index2{};
// Process complete number 1
while ((number2 > 0) && (index2 < MaxNumberOfBits)) {
binArray2[index2] = number2 % 2;
number2 /= 2;
++index2;
}
// Now, calculate the result. Here, we will store result
unsigned int binResult[MaxNumberOfBits+1] = {};
// Go over all bits
// Use carry bit
unsigned int carryBit{};
// Get maximunm index to avoid to do unessary work
const unsigned int maxIndex = ((index1 > index2) ? index1 : index2) + 1;
// Add all single bits
for (unsigned int i{}; i < maxIndex; ++i) {
// Add bit from each number + carry bit
binResult[i] = binArray1[i] + binArray2[i] + carryBit;
// Calculate the carray bit
carryBit = (binResult[i] > 1) ? 1U : 0U;
// Handle overflow
binResult[i] %= 2;
}
// Output in reverse order
std::cout << "\nResult: ";
for (unsigned int i{ maxIndex+1 }; i > 0; --i) {
std::cout << binResult[i-1];
}
std::cout << "\n\n";
}
else {
std::cerr << "\n\n*** Error: Could not read the 2 integers\n";
}
return 0;
}

Answer 2

1.
for (i = i - 1; i >= 0; i--)
{
for (j = j - 1; j >= 0; j--)
{
sumBin[k] = d1[i] + d2[j];
}
}
The i and j in this loop are both -1, so they did not enter the loop.
2.
cout << "zahl1 + zahl2 : " << sumBin << " (" << sumDez << ") \n";
The sumBin you output is the address, not the content. So the value is different every time。