C++ String Exercises: Print an integer with commas as thousands separators

Last update on April 11 2025 12:47:37 (UTC/GMT +8 hours)

29. Print an Integer with Commas as Thousands Separators

Write a C++ program to print a given integer with commas separating the thousands.

Sample Data:
(1000) -> "1,000"
(10000) -> "10,000"
(23423432) -> " 23,423,432"

Sample Solution-1:

C++ Code:

#include <bits/stdc++.h> // Include all standard libraries

using namespace std; // Using the standard namespace

// Function to format an integer with commas as thousands separators
string test(int n) {
    string result = to_string(n); // Convert integer 'n' to a string and store it in 'result'

    // Loop to insert commas for thousands separators in the string
    for (int i = result.size() - 3; i > 0; i -= 3) {
        result.insert(i, ","); // Insert a comma after every three digits from the end
    }

    return result; // Return the formatted string
}

int main() {
    int n; // Declare an integer variable to store user input

    cout << "Input a number: ";
    cin >> n; // Input an integer from the user

    cout << "\nPrint the said integer with commas as thousands separators:\n";
    cout << test(n) << endl; // Output the formatted integer with commas
}

Sample Output:

Input a number: 
Print the said integer with commas as thousands separators:
5,000

Flowchart:

Sample Solution-2:

C++ Code:

#include <bits/stdc++.h> // Include all standard libraries

using namespace std; // Using the standard namespace

// Function to format an integer with commas as thousands separators
string test(int n) {
    string result_str = to_string(n); // Convert the integer 'n' to a string and store it in 'result_str'

    // Check if the length of the string is greater than 3 (to insert commas for thousands separators)
    if (result_str.length() > 3) {
        // Loop to insert commas for thousands separators in the string
        for (int i = result_str.length() - 3; i > 0; i -= 3) {
            result_str.insert(i, ","); // Insert a comma after every three digits from the end
        }
    }

    return result_str; // Return the formatted string
}

int main() {
    int n; // Declare an integer variable to store user input

    cout << "Input a number: ";
    cin >> n; // Input an integer from the user

    cout << "\nPrint the said integer with commas as thousands separators:\n";
    cout << test(n) << endl; // Output the formatted integer with commas
}

Sample Output:

Input a number: 
Print the said integer with commas as thousands separators:
5,000

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to format an integer by inserting commas at the thousand, million, etc., positions.
Write a C++ program that reads a number and outputs it as a string formatted with commas for thousands.
Write a C++ program to convert an integer to a comma-separated string by processing its digits in reverse.
Write a C++ program that implements a function to format a number with commas and prints the formatted result.

C++ Code Editor:

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