string permutation function

[peace357]

I am trying to write two recursive functions involving two strings, 1)CAT & 2)MAN.

My function needs to print out:
TACMAN
ATCMAN
CTAMAN
TCAMAN
ACTMAN
CATMAN

Two functions required are:
1) void string::insert(size_type position, size_type number_of_copies, char c);
2) void string::erase(size_type position, size_type n)

Other functions I may need:
3) Do I need to use a permute function and a dopermute function? How do I make the permute functions part of my program by using insert and erase?

using namespace std;
 
void string::insert(size_type position, size_type number_of_copies, char c)
{
    string s1 = "CAT";
    string s2 = "MAN";
 
        //add or insert CAT to first 3
        //add or insert MAN to last 3
            //then...
                //...add TA and insert with CMAN = "TACMAN"
                //..replace TA with AT and insert with CMAN = "ATCMAN"
                //..call erase c();
                //add CT and insert with AMAN = "CTAMAN"
                    //..replace CT with TC and insert with AMAN = "TCAMAN"
                        //..call erase c();
                        //add AC and insert with TMAN = "ACTMAN"
                        //..replace AC with CA and insert with TMAN = "CATMAN"
 
 
//postcondition: The specified number of copies of c have been 
//inserted into the string at the indicated position. 
//Existing characters that used to be at or after the given position have been shifted right 
//one spot 
}
void string::erase(size_type position, size_type n)
{
 
    // delete c[]; or c[] = NULL;
}
 
 
int main()
{
    char c[5];
 
 
  insert(,,); //First function call, so it starts at one        
}
 

Please give me ideas and suggestions. I need help in putting my idea into code as this is all new to me.

Thank you.

[RRick]

The key ideas here are: permutation and recursion. This means your insert routine must call itself. In your example, it doesn't. Take a look at the visit routine in the following link for an idea of what this means. http://www.bearcave.com/random_hacks/permute.html

In your example, only the first string is being permutated. The second one is simply added to the end of the various permutations. One idea is to keep these separate until you need to print them.

As to why you need two recursive functions, this seems to be based on a specific type of permutation algorithm. I'm not sure why you need to do this. Once again, the above link shows an example.

[peace357]

I have figured out the "permutation" part and I need help with "recursion" part.

Here are the conditions for my functions:

1) the stopping case of the function occurs when the length of first has zero characters

2) for void string::insert:
-The specified number of copies of c have been inserted into the string at the indicated position.
-Existing characters that used to be at or after the given position have been shifted right one spot.

3) for void string::erase:
-n characters have been removed from the string, beginning at the specified position.

#include <iostream>
#include <cstdlib>
#include <string.h>
#include <string>
#include <iomanip> 
 
using namespace std;
 
/*void string::insert(size_type position, size_type number_of_copies, char c)
{
    string string1 = "CAT";
    string string2 = "MAN";
        permute ("", "CAT");
        permute ("", "MAN");
    cout<<string1 + string2; //results in error.
                                                    //how to use insert?
 
 
}
void string::erase(size_type position, size_type n)
{
    //dont know what to do
}*/
void permute( string prefix, string s )
{
    if ( s.size() <= 1  )
        cout <<prefix <<s <<"\n";
    else
        for ( char *p = s.begin(); p <s.end(); p++ )
        {
            char c = *p;
            s.erase( p );
            permute( prefix + c, s );
            s.insert( p, c );
        }
 
}
int main()
{
    permute( "CAT", "MAN");
    return 0;      
}
 

Please help me! I am drowning!