Python – Insert character in each duplicate string after every K elements

Given a string and a character, insert a character after every K occurrence.

Input : test_str = ‘GeeksforGeeks’, K = 2, add_chr = “;” 
Output : [‘;GeeksforGeeks’, ‘Ge;eksforGeeks’, ‘Geek;sforGeeks’, ‘Geeksf;orGeeks’, ‘Geeksfor;Geeks’, ‘GeeksforGe;eks’, ‘GeeksforGeek;s’] 
Explanation : All combinations after adding ; after every K elements.

Input : test_str = ‘GeeksforGeeks’, K = 2, add_chr = “*” 
Output : [‘*GeeksforGeeks’, ‘Ge*eksforGeeks’, ‘Geek*sforGeeks’, ‘Geeksf*orGeeks’, ‘Geeksfor*Geeks’, ‘GeeksforGe*eks’, ‘GeeksforGeek*s’] 
Explanation : All combinations after adding * after every K elements. 

Method 1: Using loop + slicing

This is one of the ways in which this task can be performed. In this, we slice string on every Kth occurrence using string slicing and append characters between them.

Python3

# Python3 code to demonstrate working of
# Insert character after every K elements
# Using loop + string slicing


# Function to Insert character
# in each duplicate string
# after every K elements
def insertCharacterAfterKelements(test_str, K, char):
    res = []
    # using loop to iterate
    for idx in range(0, len(test_str), K):

        # appending all the results
        res.append(test_str[:idx] + char + test_str[idx:])

    return str(res)


# Driver Code
# initializing string
input_str = 'GeeksforGeeks'

# printing original string
print("The original string is : " + str(input_str))

# initializing K
K = 2

# initializing add char
add_chr = ";"

# printing result
print("The extracted strings : " +
      insertCharacterAfterKelements(input_str, K, add_chr))

Output

The original string is : GeeksforGeeks
The extracted strings : [';GeeksforGeeks', 'Ge;eksforGeeks', 'Geek;sforGeeks', 'Geeksf;orGeeks', 'Geeksfor;Geeks', 'GeeksforGe;eks', 'GeeksforGeek;s']

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

Method 2: Using (list comprehension + slicing)

This is yet another way in which this task can be performed. In this, we perform a similar task as loop difference being that list comprehension is employed as shorthand to solve this question.

Python3

# Python3 code to demonstrate working of
# Insert character after every K elements
# Using list comprehension + string slicing


# Function to Insert character
# in each duplicate string
# after every K elements
def insertCharacterAfterKelements(test_str, K, char):
    # list comprehension to bind logic in one.
    res = [test_str[:idx] + char + test_str[idx:]
           for idx in range(0, len(test_str), K)]

    return str(res)


# Driver Code
# initializing string
input_str = 'GeeksforGeeks'

# printing original string
print("The original string is : " + str(input_str))

# initializing K
K = 2

# initializing add char
add_chr = ";"

# printing result
print("The extracted strings : " +
      insertCharacterAfterKelements(input_str, K, add_chr))

Output

The original string is : GeeksforGeeks
The extracted strings : [';GeeksforGeeks', 'Ge;eksforGeeks', 'Geek;sforGeeks', 'Geeksf;orGeeks', 'Geeksfor;Geeks', 'GeeksforGe;eks', 'GeeksforGeek;s']

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