Thread: Help needed with permutation function.

This function will eventually calculate all the permutaions for a set of letter of n length. I'm stumped on whether to declare something as a string or a char or a char and a char *. Any help would be appreciated.

Code:

#include <iostream>
#include <string>

using namespace std;

char GETALLCOMBOZ(char charact,int num){

char *myArr = new char[num+1];

int numofperms;
char comboz;
bool booler = false;

    do {
    
        myArr[numofperms] = myArr[numofperms]+ 1;
      
        if (numofperms == num)
        {
         
        comboz = comboz.substr(0, num - 1)+ charact.substr(myArr[numofperms],  1);
         
        }
      
        else
        {
          
        comboz = comboz + charact.substr(myArr[numofperms],  1);
        
        }
        
        if(myArr[numofperms] != strlen(charact) + 1) 
        
        {
                                     
            if(numofperms!= num)
                {
                
                numofperms = numofperms + 1;
                
                }
                
             else
               {
             
               cout << comboz;
               }
        
         else
         {
            
            if (numofperms == 1)
            
                {
              
                booler = true;
                }
           
             else {
            
                myArr[numofperms] = 0;
             
                numofperms = numofperms - 1;
             
                comboz = comboz.substr(0, numofperms - 1);
                }
     
        }
        
        
        }while (booler != true);
        
        
        }

well .substr works on strings, but strlen() works on char *'s. The std::string equivilent to strlen() is s.length() or s.size(). Your code confused me, so I am just going to give you the stl style answer

Code:

#include<iostream>
#include<string>
#include<algorithm>

void allperm(std::string s) {
	std::sort(s.begin(),s.end());
	do {
		std::cout << s << std::endl;
	} while(std::next_permutation(s.begin(),s.end()));
}

Good luck on strings longer than about 10 characters or so.

Originally Posted by grib

well .substr works on strings, but strlen() works on char *'s. The std::string equivilent to strlen() is s.length() or s.size(). Your code confused me, so I am just going to give you the stl style answer

Code:

#include<iostream>
#include<string>
#include<algorithm>

void allperm(std::string s) {
	std::sort(s.begin(),s.end());
	do {
		std::cout << s << std::endl;
	} while(std::next_permutation(s.begin(),s.end()));
}

Good luck on strings longer than about 10 characters or so.

That doesn't give all combinations, for ex. for a string "asd" all combos would be

aaa
aas
aad
asa
ada
saa
daa
sss
ssa
.....
.....
etc....

> and then use Salem's next_permutation loop on each.
Hey, don't pin this on me
<bart>I didn't do it</bart>

This is an attempt at porting VB code, here's the VB code and my attempt at the C++. It does compile but not doing the job.

Code:

Private Sub command1_Click()

    BOOLER = False
  GETALLCOMBOZ charz, 3   ' 4 = number of character combinations to try
  
End Sub

Public Sub GETALLCOMBOZ(ByVal charact As String, _
                  ByVal num As Byte)

    ReDim myarray(num)
    Do While Not (BOOLER)
 
        myarray(numofperms) = myarray(numofperms) + 1
        If numofperms = num Then
            comboz = Left$(comboz, num - 1) + Mid$(charact, myarray(numofperms), 1)
         Else
            comboz = comboz + Mid$(charact, myarray(numofperms), 1)
        End If
        If myarray(numofperms) <> Len(charact) + 1 Then
            If numofperms <> num Then
                numofperms = numofperms + 1
             Else
               Print #1, comboz
            End If
         Else
            If numofperms = 1 Then
                BOOLER = True
             Else
                myarray(numofperms) = 0
                numofperms = numofperms - 1
                comboz = Left$(comboz, numofperms - 1)
            End If
        End If
    Loop
    Close #1

End Sub

Code:

#include <iostream>
#include <string>
#include <conio.h>
#include <fstream>

using namespace std;

char *GetAllCombinations(string charact,int num);

int main(){
    
    GetAllCombinations("abcd",3);
    // for example  aaa, aab, aac, aad, aba, aca, ada, baa, caa, daa
}



char *GetAllCombinations(string charact,int num){
// redim array to size num     
char *myArr = new char[num];
// init vars
int numofperms = 0;
string comboz;
bool booler = false;
// open file for writing too
ofstream a_file ( "c:\\windows\\desktop\\comboz.txt" );
// start combinations loop

    do {
        
        myArr[numofperms] = myArr[numofperms]+ 1;
        
        if (numofperms == num)
        { 
              
        comboz = comboz.substr(0, num - 1)+ charact.substr(myArr[numofperms],  1);
        }
        else
        {
        comboz = comboz + charact.substr(myArr[numofperms],  1);
       
        }
       
        if(myArr[numofperms] != charact.length() + 1) 
        
        {
             if(numofperms!= num)
             {
             numofperms = numofperms + 1;
             }
             else
             {
             cout << comboz;
             a_file<< comboz ;
             }
         }
         else
         {
             if (numofperms == 1)
             {
             booler = true;
             }
             else 
             {
             myArr[numofperms] = 0;
             numofperms = numofperms - 1;
             comboz = comboz.substr(0, numofperms - 1);
             }
     
          }
        
        }while (booler != true);
        a_file.close();
}

If anybody could work out whats wrong with my C++ then cheers.

Originally Posted by dwks

A segmentation fault, I'd guess. Because myArr isn't initialized to zero like you assume it to be.

how do i do that ?

Since myArr is an array of chars you can use memset. I would use a vector instead of a dynamic array, though, which allows you to initialize all values to 0 in the constructor.

Originally Posted by Daved

Since myArr is an array of chars you can use memset. I would use a vector instead of a dynamic array, though, which allows you to initialize all values to 0 in the constructor.

any chance of writing it, it must be nearly there ?

groan... this is like pulling teeth..

i thikn its this section here,

Code:

char GetAllCombinations(string charact,int num);

int main(){
    
    GetAllCombinations("abcd",3);
    // for example  aaa, aab, aac, aad, aba, aca, ada, baa, caa, daa
}


char GetAllCombinations(string charact,int num){

char *myArr = new char[num];  // think this is wrong

int numofperms = 0;
string comboz;        ' string or char ?
bool booler = false;


    do {
        
        myArr[numofperms] ++;
        
        if (numofperms == num)
        { 
              
        comboz = comboz.substr(0, num - 1)+ charact.substr(myArr[numofperms],  1);
        }
        else
        {
        comboz += charact.substr(myArr[numofperms],  1);
       
        }

any thoughts?

groan... this is like pulling teeth..

Welcome to programming.

http://mathworld.wolfram.com/Combination.html

Maybe this?

http://paul.rutgers.edu/~rhoads/Code/code.html