C++ Exercises: Compute the sum of two given binary strings

Last update on August 19 2025 05:35:10 (UTC/GMT +8 hours)

22. Sum of Two Binary Strings

Write a C++ program to compute the sum of a pair of binary strings. Binary strings will be returned, and input strings shouldn't be blank or contain just 1 or 0 characters.

Sample Input: bstr1 = "10"
bstr2 = "1"
Sample Output: 10 + 1 = 11

Sample Input: bstr1 = "1100"
bstr2 = "1010"
Sample Output: 1100 + 1010 = 10110

Sample Solution:

C++ Code :

#include <iostream>

using namespace std;

// Function to add two binary strings
string binary_add(string bstr1, string bstr2) {
    // Determine the size of the result string
    int size = max(bstr1.size(), bstr2.size());
    int temp = 0;

    // Initialize an empty string to store the result
    string result_str = "";

    // Loop through each position of the binary strings and perform addition
    for (auto i = 0; i < size; ++i) {
        // Extract individual digits of binary strings
        int digit1 = (i + 1 <= bstr1.size()) ? bstr1[bstr1.size() - 1 - i] - '0' : 0;
        int digit2 = (i + 1 <= bstr2.size()) ? bstr2[bstr2.size() - 1 - i] - '0' : 0;

        // Calculate the sum of digits along with the carry
        int number = (digit1 + digit2 + temp);
        temp = number / 2;

        // Append the sum digit to the result string
        result_str = to_string(number % 2) + result_str;
    }

    // If there's a remaining carry, add it to the result
    if (temp > 0) {
        result_str = to_string(temp) + result_str;
    }

    return result_str; // Return the final result
}

// Main function to test binary_add function
int main() {
    string bstr1 = "10";
    string bstr2 = "1";
    cout << "\n" << bstr1 << " + " << bstr2 << " = " << binary_add(bstr1, bstr2) << endl;

    bstr1 = "1100";
    bstr2 = "1010";
    cout << "\n" << bstr1 << " + " << bstr2 << " = " << binary_add(bstr1, bstr2) << endl;

    bstr1 = "10";
    bstr2 = "10";
    cout << "\n" << bstr1 << " + " << bstr2 << " = " << binary_add(bstr1, bstr2) << endl;

    return 0;
}

Sample Output:

10 + 1 = 11

1100 + 1010 = 10110

10 + 10 = 100

Flowchart:

$Flowchart: Compute the sum of two given binary strings$

For more Practice: Solve these Related Problems:

Write a C++ program to add two binary strings without converting them to integers, by simulating binary addition.
Write a C++ program that processes two binary strings and outputs their sum by iterating from the least significant bit.
Write a C++ program to implement binary string addition using recursion to handle the carry propagation.
Write a C++ program that reads two binary strings, aligns them by padding zeros, and then performs digit-by-digit addition to output the result.

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