Loop with recursion

#1

i am facing difficulty in understading loop with recursion
could you give the better explanation for this

#2

this can be best understood by making the recursion tree and trying to dry run for different values of i , j

i`ll explain the recursion tree
i/p -> abc

for(int j = i ; in[j] != '\0'; j++){
   swap(in[i] , in[j]);
permute( in , i+1 ) ;
   swap(in[i] , in[j] ) ;
}

now i = 0
j = 0
swap 0,0
then call permute(in , 1 ) now the for loop starts with j = i so j= 1
swap 1 ,1
call on permute(in , 2) now for starts with j = i so j = 2
swap ( 2, 2) call for i+1 call on permute( in , 3)
now loop does execute
since in[j] == ‘\0’
the char array is still abc
now stack trace is returned to previous state
so now u are on i = 2 , j now increments now in[j] == ‘\0’
so again traced back
now i = 1 j = 2
swap( in[1] , in[2])
calll in permute ( in , i+1) ie permute(in , 2)

and soo on

#3

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