# Converting Number to String in C++

• Difficulty Level : Medium
• Last Updated : 03 Aug, 2022

Converting numbers to string or vice-versa is actually a big paradigm shift in itself. In general or more specifically in competitive programming there are many instances where we need to convert a number to a string or string to a number. But lack of knowledge of certain essential tools binds us to do so. Some methods to achieve this task are mentioned in this article.

## Converting Number to String in C++

There are 3 major methods to convert a number to a string, which are as follows:

• Using string Stream
• Using to_string()
• Using boost lexical cast

### Method 1: Using string streams

In this method, a string stream declares a stream object which first inserts a number, as a stream into an object and then uses “str()” to follow the internal conversion of a number to a string.

Example:

## CPP

 `// C++ code to demonstrate string stream method` `// to convert number to string.` `#include` `#include   // for string streams` `#include   // for string` `using` `namespace` `std;` `int` `main()` `{` `    ``int` `num = 2016;`   `    ``// declaring output string stream` `    ``ostringstream str1;`   `    ``// Sending a number as a stream into output` `    ``// string` `    ``str1 << num;`   `    ``// the str() converts number into string` `    ``string geek = str1.str();`   `    ``// Displaying the string` `    ``cout << ``"The newly formed string from number is : "``;` `    ``cout << geek << endl;`   `    ``return` `0;` `}`

Output

`The newly formed string from number is : 2016`

Time Complexity: O(n)

Auxiliary Space: O(n)

### Method 2: Using to_string()

The function to_string() accepts a number(which can be any data type) and returns the number in the desired string.

## CPP

 `// C++ code to demonstrate "to_string()" method` `// to convert number to string.` `#include ` `#include // for string and to_string()` `using` `namespace` `std;`   `// Driver Code` `int` `main()` `{` `    ``// Declaring integer` `    ``int` `i_val = 20;`   `    ``// Declaring float` `    ``float` `f_val = 30.50;`   `    ``// Conversion of int into string using` `    ``// to_string()` `    ``string stri = to_string(i_val);`   `    ``// Conversion of float into string using` `    ``// to_string()` `    ``string strf = to_string(f_val);`   `    ``// Displaying the converted strings` `    ``cout << ``"The integer in string is : "``;` `    ``cout << stri << endl;` `    ``cout << ``"The float in string is : "``;` `    ``cout << strf << endl;`   `    ``return` `0;` `}`

Output

```The integer in string is : 20
The float in string is : 30.500000```

Time Complexity: O(n)

Auxiliary Space: O(n)

### Method 3: Using boost lexical cast

Similar to string conversion, the ” lexical_cast() ” function remains the same, but in ‘boost lexical cast‘ time argument list modifies to “lexical_cast(numeric_var).

Example:

## CPP

 `// C++ code to demonstrate "lexical_cast()" method` `// to convert number to string.` `#include // for lexical_cast()` `#include ` `#include // for string` `using` `namespace` `std;`   `// Driver Code` `int` `main()` `{` `    ``// Declaring float` `    ``float` `f_val = 10.5;`   `    ``// Declaring int` `    ``int` `i_val = 17;`   `    ``// lexical_cast() converts a float into string` `    ``string strf = boost::lexical_cast(f_val);`   `    ``// lexical_cast() converts a int into string` `    ``string stri = boost::lexical_cast(i_val);`   `    ``// Displaying string converted numbers` `    ``cout << ``"The float value in string is : "``;` `    ``cout << strf << endl;` `    ``cout << ``"The int value in string is : "``;` `    ``cout << stri << endl;`   `    ``return` `0;` `}`

Output

```The float value in string is : 10.5
The int value in string is : 17```

## C++

 `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``int` `n=12234; ` `    ``char` `str; ` `  ``sprintf``(str,``"%d"``, n); ` `  ``printf``(``"the string is : %s"``,str);` `   `  `    ``return` `0;` `}`

Output

`the string is : 12234`

Time Complexity: O(n)

Auxiliary Space: O(n)

This article is contributed by Manjeet Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above.

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