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-   -   All possible combinations of a string (http://www.go4expert.com/articles/combinations-string-t227/)

anjanesh 27Dec2004 17:17

All possible combinations of a string
 
All possible combinations of a string
1. Finds all possible cominations of a given string. The total number of combinations with recurrences is the factorial of the string length.
2. Have given the word 'post' as an example since if I included a cin >> word; then a user may unconscientiously enter a long word which will take toooo long to end. To change to another word change the string str.
3. A 9 letter word like 'aeroplane' can take around 40 seconds on a 1GHz machine. A 10 letter word will take 9 x 40 s - thats 6 mins! So watch out for the string length.
4. This may time according to the length of the string str

Code: CPP

// Combination

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

unsigned long fact(unsigned long); // finds factorial of a number
void swap(int[],int,int);
void display(int[],char[]);
void Add(int[],int);

void main()
{
    // clrscr(); // Remove the first comment tag if running in TC++ or BC++ DOS mode
    int j,k,n;
   
    unsigned long i;
    char str[]="post"; // small word
    n=strlen(str);
    int*key=new int[n+1];
    key[0]=n; // key[0] contains the total no: of letters
    for (i=1;i<=key[0];i++)
        key[i]=i;
    display(key,str);
    swap(key,key[0],key[0]-1);
    display(key,str);
    for (i=3;i<=fact(key[0]);i+=2)
    {
        for (j=key[0]-1;j>=0;j--)
        {
            if ((i-1)%fact(j)==0)
            {
                Add(key,key[0]-j);
                for (k=1;k<=key[0]-j-1;k++)
                    if (key[k]==key[key[0]-j])
                    {Add(key,key[0]-j);k=0;}
            }
        }
        display(key,str);
        swap(key,key[0],key[0]-1);
        display(key,str);
    }
    cout << "\nTotal no: of combinations = " << key[0] << "! = " << i-1;
    getch();
}

unsigned long fact(unsigned long f)
{
    return f==0?1:f*fact(f-1);
}

void swap(int k[],int a,int b)
{
    int t=k[a];k[a]=k[b];k[b]=t;
}

void display(int k[],char s[])
{
    for(int i=1;i<=k[0];i++)
        cout << s[k[i]-1];
    cout << '\t';
}

void Add(int k[],int i)
{
    k[i]++;
    if (k[i]==k[0]+1)
        k[i]=1;
}


shabbir 27Dec2004 18:14

Re: All possible combinations of a string
 
First of all welcome to the go4expert forums and yes a nice code also.

Can you mention which compiler it will compile as its not meant for Visual Studio as it has clrscr method.

Thanks
Shabbir Bhimani

anjanesh 28Dec2004 18:25

Re: All possible combinations of a string
 
I wrote this using TC++ 3.1.
It compiled and worked in TC++ 3.1 and Borland C++ 3.11.
Remove clrscr() and it compiles and executes in vc++6 - checked.

shabbir 28Dec2004 18:43

Re: All possible combinations of a string
 
Thats nice.

sanjit_Developer 30Dec2004 10:56

Re: All possible combinations of a string
 
Hi,
Thats an extraordinary contribution frnd.Thanx.
sanjit khasnois

jcnovoa 11Oct2005 21:13

Re: All possible combinations of a string
 
Thank you... with a little modification, I was able to make it work for my C# app that I am working on. Great code... too bad google ranks it so low in its engine

shabbir 11Oct2005 23:03

Re: All possible combinations of a string
 
Quote:

Originally Posted by jcnovoa
too bad google ranks it so low in its engine

Google is slowly loosing the share and the quality in Search domain. In sitepoint forum in some thread I read recently that within couple of years Google has lost from 90% of the share traffic to 48% and the rest have moved to Yahoo and MSN. Its probably because they are more interested in satisfying there Clients of adwords.

Alaj 20Jul2006 14:09

Re: All possible combinations of a string
 
hello
this is realy a very good code ...

can any one tell me that what is the basic process of function

void add (int[] , int);

i need its processing flow plz if anybody can help me i'll be thankful

anjanesh 20Jul2006 15:01

Re: All possible combinations of a string
 
I should've documented this when I wrote this in college 4 yrs back.
I'll try to remember and repost this code with documentation.

Alaj 21Jul2006 10:45

Re: All possible combinations of a string
 
hello
one more question is that plz tell me the logic of "if ((i-1)%fact(j)==0)" this condition in this code..
and plz send that documentation as soon as possible


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