Remove all Occurrences of Character in String in C Language

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Program-to-Remove-all-Occurrences-of-Character-in-String-in-C-Language

Program Description:

Write a Program to Remove all occurrences of character in string in C Programming Language. The program should accept a string and a character from the user and remove all occurrences of the said character from the string.

📢 This Program is part of the C String Practice Programs series

We will look at two methods to Remove all occurrences of a character in the string in C Language. Each method will contain a step-by-step explanation of the program with program output. We also included the instructions to compile and run the program using your compiler.

Before going to look at the program, Let’s quickly check the excepted input and output of the program

Example Input and Output:

Input:

Enter a string : go go go go george

Enter character to remove from the string: g

Output:

String Before Removing All occurrences of character : go go go go george

String After Removing All Occurrences of character('g') : o o o o eore

The program removed all occurrences of the character g and returned the resultant string.

📢The program is case-sensitive. So the Uppercase characters and Lowercase characters are different.

Prerequisites:

It is recommended to know the basics of the string, function and how to pass string to functions. Please go through the following tutorials to learn more about these topics.

We will look at the two different methods to Remove all occurrences of character in a string in C Language.

  • Iterative Method to Remove all occurrence of a character from string
  • User-defined Functions to remove characters

Remove All Occurrences of Character in String in C Program Explanation:

Here are the step-by-step explanation for the program.

  1. Start the program by creating a macro named SIZE. This macro holds the max size of the string- #define SIZE 100
  2. Declare the input string( inputStr) and character to search( ch).
  3. Take the input string and character to search from the user and update the inputStr and ch variables respectively. We use the gets function to read the string.
  4. Calculate the length of the input string inputStr and store it in length variable.
  5. Now, To Remove all occurrences of the character( ch) in a string( inputStr), Traverse over the input string, and find the position or index( i) of each occurrence of the character in the string. For each occurrence move all characters from the right side of the index i to one position left. ( i.e shift all characters to one place left)
  6. Create a Loop to find all occurrences of the character in the string. The For loop starts by initializing variable i to 0. It will continue looping as long as the present character ( inputStr[i]) is not a NULLcharacter ( '\0').
    • At each iteration, Check if the current character is equal( inputStr) to target character( ch). – i.e if(inputStr[i] == ch)
    • If the above condition is true, Then move all characters from the right side of the iindex to one position left. To do this, Create a While loop and run it till the j < strlen(inputStr) condition is true. (where j = i;)
      • At each iteration of the while loop, Copy the character at the index j+1 to index j- i.e inputStr[j] = inputStr[j+1];
      • Increment the index j by 1. – j++;
    • Otherwise, i.e if(inputStr[i] == ch) condition is false, Then continue to the next iteration to find the next occurrence of the character ch.
  7. Once the above Step 6 is completed, Then all occurrences of the character ch will be removed from the input string inputStr. Display the resultant string on the console.
  8. Stop the program.

Program to Remove All Occurrences of Character in String in C – Iterative Method:

Program to remove a characters from the string in the c programming language.

We need to include the string.h header file to use the strlen() library function. We can also implement custom string length function as well.

Program Output:

Compile the program using your favorite compiler. We are using the GCC compiler on ubuntu linux OS.

Here are the instructions to Compile and Run the C Programs in Linux.

$ gcc remove-all.c

Run the program. The above command generates an exectuable file called a.out on linux OS and .exe file on windows OS. Run the executable file.

remove-all-occurrences-of-character-from-string-in-c-program-output

As we can see from the above output, The all occurrences of the character o is removed from the input string. Let’s look another example.

In this example, The input string is AABBCCBBCCAABBAA and the character to remove is A. So the program removed all occurrences of the character B in the input string and returned the resultant string as BBCCBBCCBB

Remove All Occurrences of Character in String using a user-defined function in C:

In the above program, We have written the complete program inside the mainfunction. It is not a recommended method, Let’s rewrite the above program to use a function to remove all occurrences of given character from the string.

By using the functions we can define a function once and can call it as many times as we want. Functions also increase the readability of the program and make it easier to debug issues. Here are the benefits using the functions in programming.

Here is the Rewritten C program to remove all occurrences of the character from string

We have defined a function called removeAll() to remove all occurrences of the character. Here is the prototype/syntax of the function

void removeAll(char * inputStr, char ch)

The removeAll() function takes two formal arguments, They are inputStr(character pointer) and ch(character). The inputStr points to the string and the ch variable holds the character to be removed.

This function go through the all elements of the inputStr string and removes or deletes all occurrences of the character ch from it.

Inside the main()function, Make a call to the removeAll() function with the inputStr and ch to remove all occurrences of the ch from inputStr

Display the resultant string on the screen.

Program Output:

Let’s Compile and Run the program.

c-program-remove-characters-from-string-using-function

As we can see from the above outputs, The program is properly removing the all occurrences of the given character from the input string.

For example, All occurrences of the character e has been removed from the input string Roger Federer and the resultant string is Rogr Fdrr.

More String Programs:

Venkat

Hi Guys, I am Venkatesh. I am a programmer and an Open Source enthusiast. I write about programming and technology on this blog.

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