Run Length Encoding in Python

Given an input string, write a function that returns the Run Length Encoded string for the input string. For example, if the input string is 'wwwwaaadexxxxxx', then the function should return 'w4a3d1e1x6'.

Examples:

Input  :  str = 'wwwxxxwww'
Output : 'w3x3w3'

This problem has existing solution please refer Run Length Encoding link. In the simplest approach, we iterate through the string, track the current character and count its consecutive occurrences. When a different character is encountered, we append the current character and its count to the result.

Steps:

Initialize a count variable to 1.
Traverse the string and count consecutive characters.
When the character changes, append the character and its count to the result.
If the string ends, append the last character and its count.

Implementation:

Python

# Function to perform Run-Length Encoding using a simple iterative approach
def runLengthEncodingIterative(input):
    output = ''
    
    # We start with the first character
    count = 1  
    
    # Loop through the string starting from the second character
    for i in range(1, len(input)):
      
       # If the current character is the same as the previous one
        if input[i] == input[i - 1]: 
            count += 1  # Increment the count
        else:
          
          	# Add previous character and its count to output
            output += f"{input[i - 1]}{count}"  
            
            # Reset count for the new character
            count = 1  
    
    # After the loop, we still need to add the last character group
    output += f"{input[-1]}{count}"
    
    return output

# Driver code
input = "wwwxxxwww"
print(runLengthEncodingIterative(input))  # Expected output: w3x3w3

Output

w3x3w3

Using Regular Expressions

This approach uses regex to find consecutive characters and count their occurrences.

Another code:

Python

from itertools import groupby  

# Function to perform Run-Length Encoding using itertools.groupby
def runLengthEncodingGroupby(input):
  
    # Initialize an empty string to store the final result
    output = ''
    
    # Group the string by consecutive characters and count the occurrences
    for char, group in groupby(input):
      	# Counting the occurrences of the character	
        count = len(list(group)) 
        
        # Appending the character and its count to the output string
        output += f"{char}{count}"  
    
    return output

# Driver code
input = "wwwxxxwww"
print(runLengthEncodingGroupby(input))  # Expected output: w3x3w3

Output

w3x3w3

Run Length Encoding in Python

Using Regular Expressions

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