Concatenate std::string and int in C++

Concatenate a string and an integer means, convert both the string and integer to a single string. In this article we will discuss all the approches to concatenate a std:string and an integer type using C/C++ program. First of all, let's understand the problem statement.

We are given a standard c++ string and an integer. We have to output a single string by combining the given string and integer. For example:

// Input String and Integer
"Value = "
25

// Output String
"Value = 25"

Concatenate String and Int in C++

Here is the list of approaches to concatenate string and integer using c++ program, which we will be discussing in this article with stepwise explanation and complete example codes.

• Using Stringstream Object
• Using to_string() Function

Using Stringstream to Concatenate String and Int

The stringstream is an object of string class defined in the <sstream> header file. It is used for reading from the stream strings. Now, let's see how to use stringstream to concatenate string and int.

Example

In the code below we defined a stringstream object and passed both string and integer to it. The resulting string will be combination of string and integer.

#include <iostream>
#include <sstream>
using namespace std;

int main() {
    int num = 7;
    stringstream ss;
    ss << "Item#" << num;
    string result = ss.str();
    cout << result;  
}

The output of the above code will be:

Item#7

Using to_string() to Concatenate String and Int

In this method, first we will convert integer type to string type using to_string function. Then, we can simply use the + operator to combine first string and second string. Let's see how to implement this method using an example

Example

In the code below, used to_string function to convert 5 to the string "5". Then we used + operator to add "Count: " string and "5".

#include <iostream>
using namespace std;

int main() {
    string s = "Count: ";
    int num = 5;
    s += to_string(num);
    cout << s; 
}

The output of the above code will be:

Count: 5