CODEWITHSUNDEEP
regex
user2852075
user2852075

Reputation: 21

Match for words that have same letters

I am trying to match words that have the same letter repeated as the second letter, the ending character and an in the middle 1 times, and I need to capture the second letter and match the whole line.

words examples

syzygy
error
banana

I tried doing 

^[a-z]([a-z])[a-z]+[a-z]+\1$

and this matches the lines and captures my second letter, but I need to make sure the second letter is repeated

 s(y)z y <-same as second character g y <- ends in same character

so I need to be sure in a string that y is at the second position, 1 time in the middle, and ending of the string

Upvotes: 2

Views: 1008

Answers (3)

anubhava
anubhava

Reputation: 784998

You can use this regex:

^.(.).*?\1.*?\1$

Upvotes: 1

hwnd
hwnd

Reputation: 70722

One way you could do this, if I understand you correctly is using a negative look ahead.

^.(.)(?:(?!\1).)*\1(?:(?!\1).)*\1$

The dot . matches any single character, except line break characters. By using \1, we reference the match that was saved in the first capture group.

See regular expression explanation

See live demo of capturing the second character and matching the whole string.

See live demo of how \1 is matching repeated characters.

Upvotes: 1

user557597
user557597

Reputation: 

 # ^[a-z]([a-z])[a-z]*\1[a-z]*\1$

 ^ 
 [a-z]  
 ( [a-z] )   # (1), Second letter
 [a-z]* 
 \1          # A Backref to second letter in the middle
 [a-z]* 
 \1          # A Backref to second letter at the end
 $

Upvotes: 1

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