How to Replace a Substring in a String with Another String in C Without Using string.h

Learn how to replace a substring in a C string without using string.h. Follow this comprehensive guide with step-by-step instructions and sample code to master substring replacement.
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How to Replace a Substring in a String with Another String in C Without Using <string.h>

In C programming, manipulating strings can sometimes be quite a task, especially when you want to perform actions like replacing a substring with another string. If you're starting your journey in C and want to learn how to do this without using the <string.h> library, you've come to the right place. In this guide, we'll walk you through a simple and effective method for replacing substrings within a string with detailed explanations and sample code.

Understanding the Problem

The task is to replace a substring in a given string. For example, suppose we have the string "123abc890" and we want to replace the substring "abc" with "xyz", resulting in "123xyz890". Furthermore, this solution should avoid using the functions provided in <string.h>. Implementing this takes a bit of creativity since we have to manage string operations manually.

A Walkthrough of the Solution

Step 1: Setting Up the Environment

To commence, we need to create a function for replacing the substring. This function will take in our destination string, the original string, the substring to be replaced, and the new substring as parameters. Here's the foundation of our function:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Iterating Through the Characters

We will iterate through each character of the original string, checking for matches with the substring we want to replace. This loop will help us build our resultant string character by character:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Checking for Matches

Inside the loop, we will create another loop to check whether the substring "str2" matches at the current position in "str1". If a match is found, we will copy the new substring (str3) into our destination string:

[[See Video to Reveal this Text or Code Snippet]]

If str2[j] is '\0', it confirms that we've found a complete match.

Step 4: Copy the Replacement

Once a match is confirmed, we need to copy the new string (str3) into our destination string and skip the length of the substring str2 in the original string:

[[See Video to Reveal this Text or Code Snippet]]

Step 5: Null Termination

It’s important to terminate our destination string properly so that it is a valid C string:

[[See Video to Reveal this Text or Code Snippet]]

Step 6: Full Implementation

Here is the complete code that combines all the above steps:

[[See Video to Reveal this Text or Code Snippet]]

Sample Output

After running the code, you will get the following output:

[[See Video to Reveal this Text or Code Snippet]]

The output proves that we've successfully replaced the substring.

Conclusion

Learning how to replace a substring in C without using <string.h> is a great way to understand string manipulation at a deeper level. As you practice this method, it can enhance your coding skills and help you solve similar problems more efficiently.

We hope this guide has clarified the steps needed to achieve string replacement in C. Happy coding!