Not able to understand string permutation Java code

Question

I have this working code to print string permutations without repetitions, but not able to wrap my head around how is it working as in logic. Any suggestions will be really

Answer 1

 for (int i = 0; i < input.length(); i++) {

The above for loop is doing the magic

Input ABCD

Iterations

input: BCD sofar: A .... recursion goes on

input: ACD sofar: B ....

input: ABD sofar: C ....

input: ABC sofar: D .....

Hope this helps