duplicate input string

Author: sachuverma

DSA Crack Sheet/README.md

@@ -57,6 +57,7 @@
 
 - [Reverse String](https://leetcode.com/problems/reverse-string/ "view question") - [Cpp Solution](./solutions/Reverse%20String.cpp)
 - [Palindrome String](https://practice.geeksforgeeks.org/problems/palindrome-string0817/1 "view question") - [Cpp Solution](./solutions/Palindrome%20String.cpp)
+- [Print all the duplicates in the input string](https://www.geeksforgeeks.org/print-all-the-duplicates-in-the-input-string/ "view topic")
 - []( "view question") - [Cpp Solution](./solutions/.cpp)
 
 ### Searching & Sorting