# Python – Longest Substring Length of K

Given a String and a character K, find longest substring length of K.

Input : test_str = ‘abcaaaacbbaa’, K = b
Output : 2
Explanation : b occurs twice, 2 > 1.

Input : test_str = ‘abcaacccbbaa’, K = c
Output : 3
Explanation : Maximum times c occurs is 3.

Method #1 : Using loop

This is brute way to solve this problem, in this, when K is encountered, counter is maintained till other character occurs, and count is noted, the maximum of these counts is kept and is returned as result.

## Python3

 `# Python3 code to demonstrate working of  ` `# Longest Substring of K ` `# Using loop ` ` `  `# initializing string ` `test_str ``=` `'abcaaaacbbaa'` ` `  `# printing original String ` `print``(``"The original string is : "` `+` `str``(test_str)) ` ` `  `# initializing K  ` `K ``=` `'a'` ` `  `cnt ``=` `0` `res ``=` `0` `for` `idx ``in` `range``(``len``(test_str)): ` `     `  `    ``# increment counter on checking ` `    ``if` `test_str[idx] ``=``=` `K: ` `        ``cnt ``+``=` `1` `    ``else``: ` `        ``cnt ``=` `0` `         `  `    ``# retaining max ` `    ``res ``=` `max``(res, cnt) ` ` `  `# printing result  ` `print``(``"The Longest Substring Length : "` `+` `str``(res))  `

Output

```The original string is : abcaaaacbbaa
The Longest Substring Length : 4
```

Method #2 : Using findall() + max()

In this, we get all the possible substrings of K using findall() and max() is used over it to get maximum length with len as key.

## Python3

 `# Python3 code to demonstrate working of  ` `# Longest Substring of K ` `# Using findall() + max() ` `import` `re ` ` `  `# initializing string ` `test_str ``=` `'abcaaaacbbaa'` ` `  `# printing original String ` `print``(``"The original string is : "` `+` `str``(test_str)) ` ` `  `# initializing K  ` `K ``=` `'a'` ` `  `# getting all substrings ` `res ``=` `re.findall(r'``' + K + '``+``', test_str) ` ` `  `# getting maximum of substrings Length ` `res ``=` `len``(``max``(res, key ``=` `len``)) ` ` `  `# printing result  ` `print``(``"The Longest Substring Length : "` `+` `str``(res))  `

Output

```The original string is : abcaaaacbbaa
The Longest Substring Length : 4
```

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