Python | Longest Run of given Character in String

Sometimes, while working with Strings, we can have a problem in which we need to perform the extraction of length of longest consecution of certain letter. This can have application in web development and competitive programming. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop
This is brute force method in which we can perform this task. In this, we run a loop over the String and keep on memorizing the maximum whenever the run occurs.

# Python3 code to demonstrate working of
# Longest Run of Character in String
# Using loop

# initializing string
test_str = 'geeksforgeeeks'

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

# initializing K
K = 'e'

# Longest Run of Character in String
# Using loop
res = 0
cnt = 0
for chr in test_str:
    if chr == K:
        cnt += 1
    else:
        res = max(res, cnt)
        cnt = 0
res = max(res, cnt)

# printing result
print("Longest Run length of K : " + str(res))

Output :

The original string is : geeksforgeeeks
Longest Run length of K : 3

Method #2 : Using max() + re.findall()
This is one liner way in which this problem can be solved. In this, we find the maximum of all runs found using findall().

# Python3 code to demonstrate working of
# Longest Run of Character in String
# Using max() + re.findall()
import re

# initializing string
test_str = 'geeksforgeeeks'

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

# initializing K
K = 'e'

# Longest Run of Character in String
# Using max() + re.findall()
res = len(max(re.findall(K + '+', test_str), key = len))

# printing result
print("Longest Run length of K : " + str(res))

Output :

The original string is : geeksforgeeeks
Longest Run length of K : 3