Python | Replace multiple occurrence of character by single

Given a string and a character, write a Python program to replace multiple occurrences of the given character by a single character. Examples:

Input : Geeksforgeeks, ch = 'e'
Output : Geksforgeks

Input : Wiiiin, ch = 'i'
Output : Win

Approach #1 : Naive Approach This method is a brute force approach in which we take another list ‘new_str’. Use a for loop to check if the given character is repeated or not. If repeated multiple times, append the character single time to the list. Other characters(Not the given character) are simply appended to the list without any alteration. 

Python3

# Python program to replace multiple
# occurrences of a character by a single character

def replace(s, ch):
    new_str = []
    l = len(s)

    for i in range(len(s)):
        if (s[i] == ch and i != (l-1) and
           i != 0 and s[i + 1] != ch and s[i-1] != ch):
            new_str.append(s[i])

        elif s[i] == ch:
            if ((i != (l-1) and s[i + 1] == ch) and
               (i != 0 and s[i-1] != ch)):
                new_str.append(s[i])

        else:
            new_str.append(s[i])

    return ("".join(i for i in new_str))


# Driver code
s = 'Geeksforgeeks'
char = 'e'
print(replace(s, char))

Output:

Geksforgeks

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

Approach #2 : Using Python Regex 

Python3

import re

# Function to replace multiple occurrences
# of a character by a single character
def replace(string, char):
    pattern = char + '{2,}'
    string = re.sub(pattern, char, string)
    return string

# Driver code
string = 'Geeksforgeeks'
char = 'e'
print(replace(string, char))

Output:

Geksforgeks

Time Complexity: O(N)
Auxiliary Space: O(1)