C++ Exercises: Calculate the product of two positive integers represented as strings

C++ Math: Exercise-20 with Solution

Write a C++ program to calculate the product of two positive integers represented as strings. Return the result as a string.

Sample Input: sn1 = "12"
sn2 = "5"
Sample Output: 12 X 5 = 60

Sample Input: sn1 = "48"
sn2 = "85"
Sample Output: 48 X 85 = 4080

Sample Solution:

C++ Code :

#include <iostream>
#include <algorithm>
#include <vector>
#include <functional>

using namespace std; 

// Function to multiply two numbers represented as strings
string multiply(string sn1, string sn2) {
    // Lambda function to convert character to integer value
    const auto char_to_int = [](const char c) { return c - '0'; };
    // Lambda function to convert integer to character value
    const auto int_to_char = [](const int i) { return i + '0'; };

    // Convert string representation of numbers to integer vectors in reverse order
    vector<int> n1;
    transform(sn1.rbegin(), sn1.rend(), back_inserter(n1), char_to_int);
    vector<int> n2;
    transform(sn2.rbegin(), sn2.rend(), back_inserter(n2), char_to_int);

    // Create a temporary vector to store intermediate multiplication results
    vector<int> temp(n1.size() + n2.size());

    // Perform multiplication of numbers digit by digit
    for(int i = 0; i < n1.size(); ++i) {
        for(int j = 0; j < n2.size(); ++j) {
            temp[i + j] += n1[i] * n2[j];
            temp[i + j + 1] += temp[i + j] / 10;
            temp[i + j] %= 10;
        }
    }

    // Convert the temporary vector to string representation of the result
    string result;
    transform(find_if(temp.rbegin(), prev(temp.rend()),
                     [](const int i) { return i != 0; }),
              temp.rend(), back_inserter(result), int_to_char);
    return result;
}

// Main function to test the multiply function
int main()  
{  
    // Test cases for multiplying two numbers represented as strings
    string sn1 = "12";
    string sn2 = "5";    
	cout << sn1 <<" X " << sn2 << " = " << multiply(sn1, sn2) << endl;
    sn1 = "48";
    sn2 = "85";    
	cout << sn1 <<" X " << sn2 << " = " << multiply(sn1, sn2) << endl;	
    return 0;  
}

Sample Output:

12 X 5 = 60
48 X 85 = 4080

Flowchart:

C++ Code Editor:

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