Need a GREP help

[Nousheeth]

I want to replace Double character to single character 

Example

AA to A

BB to B

CC to C

DD to D

GG to G

So I use the parenthesis to find the character by group like (AA)|(BB)|(CC)|(DD)|(GG)

What i need to mention as a Change.

I tried with A$1,B$2,C$3,D$4

But is not working, I can undestand my method is wrong.

help me to find the right solution 

Thankyou

[m1b · Accepted solution]

Try using:

(\w)\1

for your grep pattern. The trailing \1 is a back reference to the character captured in group 1 (in parentheses) so it matches two of the same character.

In your changeTo you can use $1 to refer to that same character.

[jctremblay · Accepted solution]

Find: (\u)\1
Change: $1

[Peter Kahrel · Accepted solution]

You already have two correct answers, and here's another approach. A bit different, in theory a bit more efficient:

Find: (\w)(?=\1)

Replace: <leave blank>

It deletes a word character only if it's followed by its duplicate.

[jctremblay · Accepted solution]

And here a forth and fifth ways to do it...

Find: (\u)\K\1
Replace: <leave blank>

Find: (?<=(\u))\1
Replace: <leave blank>

[Peter Kahrel]

Spoilt for choice!

[Nousheeth]

Thankyou all for the right Answer.