Regular expressions or what we can call regex for short are sequences of symbols and characters that create a search pattern and help us to find specific patterns within a given text. In this article, we will learn how to replace text in a string using regex in C++.

Example

Input:
str = "Hello, World! Hello, GFG!" ; 
text = "Hello";
replace= "Hi";

Output:
Hi, World! Hi, GFG!

Replace Regex Matches in C++ String

To replace a text in a string using regex, we can use the function std::regex_replace(). It is defined inside the <regex> header so we need to include it in our program.

Algorithm

1. Define the main string, string to be replaced and replacement string.
2. Create a regex object of the string you want to replace.
3. Then pass the main string, regex object and replacement string to the regex_replace() function.
4. The function regex_replace() returns a new string with the replacements applied.

C++ Program to Replace Text in a String Using Regex

Original: Hello, World! Hello, GFG!
Modified: Hi, World! Hi, GFG!

Time Complexity: O(N)
Auxiliary Space: O(N)