HackerRank Python Solution - Regex and Parsing - Group(), Groups() & Groupdict()

group():

• A group() expression returns one or more subgroups of the match.

>>> import re
>>> m = re.match(r'(\w+)@(\w+)\.(\w+)','username@hackerrank.com')
>>> m.group(0)       # The entire match 
'username@hackerrank.com'
>>> m.group(1)       # The first parenthesized subgroup.
'username'
>>> m.group(2)       # The second parenthesized subgroup.
'hackerrank'
>>> m.group(3)       # The third parenthesized subgroup.
'com'
>>> m.group(1,2,3)   # Multiple arguments give us a tuple.
('username', 'hackerrank', 'com')

groups():

• A groups() expression returns a tuple containing all the subgroups of the match.

>>> import re
>>> m = re.match(r'(\w+)@(\w+)\.(\w+)','username@hackerrank.com')
>>> m.groups()
('username', 'hackerrank', 'com')

groupdict():

• A groupdict() expression returns a dictionary containing all the named subgroups of the match, keyed by the subgroup name.

>>> m = re.match(r'(?P<user>\w+)@(?P<website>\w+)\.(?P<extension>\w+)','myname@hackerrank.com')
>>> m.groupdict()
{'website': 'hackerrank', 'user': 'myname', 'extension': 'com'}

Task:

• You are given a string S.
• Your task is to find the first occurrence of an alphanumeric character in S (read from left to right) that has consecutive repetitions.

Input Format:

• A single line of input containing the string S.

Constraints:

• 0 < len(S) < 100

Output Format:

• Print the first occurrence of the repeating character. If there are no repeating characters, print -1.

Sample Input:

..12345678910111213141516171820212223

Sample Output:

1

Explanation:

• .. is the first repeating character, but it is not alphanumeric.
• 1 is the first (from left to right) alphanumeric repeating character of the string in substring 111.

Solution:

import re
s = input()
m = re.search(r"([a-zA-Z0-9])\1", s)

if m:
    print(m.group(1))
else:
    print(-1)

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