Question

Write a recursive function with this prototype (using the string type from the new C++ String class):

void permute(string first, string second)
// Postcondition: The output consists of lines of Strings. Each String
// is made by writing some rearrangement of first followed by all
// of second.
// For example, if first is "CAT" and second is "MAN", then there will
// be six lines of output:
// CATMAN
// ACTMAN
// TCAMAN
// CTAMAN
// ATCMAN
// TACMAN
Hints: The stopping case occurs when the length of first is zero (in which case the function prints second).

Answer 1

Some string member functions that will help you for a String s:
s[s.length( ) - 1] is a copy of the last character of s.
s.length( ) is the length of s.
cout << s << endl; will print s.
s = c + s; will insert the character c at the front of s.
s += c; will append the character c to the end of s.
s.erase(0, 1); will remove one character from the front of s.
s.erase(s.length( )-1, 1) will remove the last character from s.


Can anyone tell me the steps on how to appproach a problem like this? What should I do first and how I double check that my recursive calls are sound?