- Write a program that will ask the user for letters. - It should accept characters until the user enters not a letter - You need to write a recursive function that prints all possible combinations of those letters. You must write at least three functions - int main() - Which is the main function. Keep it brief - A recursive function that generates all possible combinations, remember you can have loops in a recursive functions - A recursive function that will print out the a combination - You can write more functions if you wish NOTE THAT ALL STRINGS AND VECTORS BEING PASSED INTO FUNCTIONS MUST BE PASSED IN BY REFERENCE ( THIS MEANS USING \&) SAMPLE OUT Enter letters (enter not a letter to stop) qw t i7 qwti qw it qtw i q ti w q iw qitw wqti w q it wtqi wtiq wiqt witq tq w i tqiw Enter letters (enter not a letter to stop) qw t i7 qwti qwit qtwi qtiw qiwt qitw wqti wqit wtqi wtiq wiqt w it tqwi tqiw twqi twiq tiqw tiwq iq w t iqtw i w q t i w tq it q w it w