Doubt regarding how recursion goes backward

#1

for e.g abc is the input and we take a ab and then abc but after printing abc how it goes to ab ?
I am stuck in this

#2

@navin_japes,
F(a) calls F(ab) which then calls F(abc),

Now in F(abc), we hit the base case and print “abc” followed by a return statement.
After the return statement, the control comes back to F(ab) which does rest of its recursions, eventually returning back to F(a).

#3

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#4

How it goes without setting the i value to i-1 and after finishing how it goes to right that also is not clear

#5

@navin_japes,
When F(i-1) asks for result from F(i), its call is stored in a stack called recursion stack, so when execution of F(i) is finished, the control is given back to the top element of the recursion stack( which here is F(i-1) ), and thus F(i-1) gains control again.

For going “right” F(i-1) calls F(i) i,e the recursion you wrote in your code.