Python Program to Determine How Many Times a Given Letter Occurs in a String Recursively

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Recursion:

Recursion is the process by which a function calls itself directly or indirectly, and the associated function is known as a recursive function. Certain issues can be addressed fairly easily using a recursive approach. Towers of Hanoi (TOH), Inorder /Preorder/Postorder Tree Traversals, DFS of Graph, and other analogous issues are examples.

Given a string and a character the task is to count the occurrence of the given letter in the string using recursive approach in Python.

Examples:

Example1:

Input:

Enter some random string= btechgeeks
Enter some random character= e

Output:

Priting the count of e in the given string btechgeeks = 3

Example2:

Input:

Enter some random string= symphony 
Enter some random character= y

Output:

Printing the count of y in the given string symphony = 2

Program to Determine How Many Times a Given Letter Occurs in a String Recursively

Below are the ways to count the occurrence of the given letter in the string using recursive approach in Python.

Using Recursion(Static Input)
Using Recursion(User Input)

Method #1:Using Recursion(Static Input)

Approach:

Give the string and character as static input.
Pass the string and the characters to a recursive function as arguments.
Pass the fundamental constraint that the string is not empty.
If the initial character of the string is the same as the character taken from the user, increment the count.
The string is progressed in either direction, and the number of times the letter appears in the string is printed.
Exit of program.

Below is the implementation:

# function which returns count of the given character in the string recursively.


def checkCountRecursively(given_string, character):
  # Pass the fundamental constraint that the string is not empty.
    if not given_string:
        return 0
    # If the initial character of the string is the same as the character
    # taken from the user, increment the count.
    elif given_string[0] == character:
        return 1+checkCountRecursively(given_string[1:], character)
    # The string is progressed in either direction, and the number of times
    # the letter appears in the string is printed.
    else:
        return checkCountRecursively(given_string[1:], character)


# given string as static input
given_string = 'btechgeeks'
# given character as static input
given_character = 'e'
# passing the given character and given string to checkCountRecursively function
print('Priting the count of', given_character, 'in the given string',
      given_string, '=', checkCountRecursively(given_string, given_character))

Output:

Priting the count of e in the given string btechgeeks = 3

Method #2:Using Recursion(User Input)

Approach:

Scan the string and character as user input using input() function.
Pass the string and the characters to a recursive function as arguments.
Pass the fundamental constraint that the string is not empty.
If the initial character of the string is the same as the character taken from the user, increment the count.
The string is progressed in either direction, and the number of times the letter appears in the string is printed.
Exit of program.

Below is the implementation:

# function which returns count of the given character in the string recursively.


def checkCountRecursively(given_string, character):
  # Pass the fundamental constraint that the string is not empty.
    if not given_string:
        return 0
    # If the initial character of the string is the same as the character
    # taken from the user, increment the count.
    elif given_string[0] == character:
        return 1+checkCountRecursively(given_string[1:], character)
    # The string is progressed in either direction, and the number of times
    # the letter appears in the string is printed.
    else:
        return checkCountRecursively(given_string[1:], character)


# Scan some random string as user input using input() function.
given_string = input('Enter some random string= ')
# Scan some random character as user input using input() function.
given_character = input('Enter some random character= ')
# passing the given character and given string to checkCountRecursively function
print('Printing the count of', given_character, 'in the given string',
      given_string, '=', checkCountRecursively(given_string, given_character))

Output:

Enter some random string= symphony
Enter some random character= y
Printing the count of y in the given string symphony = 2

Explanation:

A string and a character must be entered by the user and stored in distinct variables.
The recursive function is given the string and the character as arguments.
The basic criterion is that the string is not empty.
The count is increased if the first character of the string matches the character taken from the user.
The string is updated by passing it back to the method recursively.
The number of times the letter appears in the string is displayed.

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