Recursion-finding twin characters in a string

#1

https://ide.codingblocks.com/#/s/29532
my code for-https://hack.codingblocks.com/contests/c/457/344

Please help me with the logic, I’ve written my doubt in the comments of the code

#2

https://ide.codingblocks.com/#/s/29550

i have solved this problem for you. Please see my code and ask if you are not able to understand anything. Use this method to solve similar recursion problems.