assignment of new string

i need to figure out a way to make the resulting 4 digit number assigned into a new string... any help would be appreciated...
also, i can't get this while statement to work??? i suck at C++!!!!

Code:

---

#include <iostream.h>
#include <stdlib.h>
#include <iomanip>
#include <string.h>

int main()

{
bool valid = false;
char initialdigit [5];
int x;
int tmp;
int firstinteger;

 cout<<"Please enter a non-zero 4 digit number..."<<endl;
 cin>> initialdigit;

 firstinteger = atoi (initialdigit);

 if (firstinteger > 0)
    valid = true;

 while (valid)
    {
    if (initialdigit [0] < initialdigit [1])
      {
        tmp = initialdigit [0];
        initialdigit [0] = initialdigit [1];
        initialdigit [1] = tmp;
        }
    if (initialdigit [1] < initialdigit [2])
        {
          tmp = initialdigit [1];
          initialdigit [1] = initialdigit [2];
          initialdigit [2] = tmp;
        }
    if (initialdigit [2] < initialdigit [3])
      {
          tmp = initialdigit [2];
          initialdigit [2] = initialdigit [3];
          initialdigit [3] = tmp;
        }

        }
valid = false;

cout<<firstinteger<<endl;


      system("PAUSE");
      return 0;
}

---

thanks guys...

The FAQ has a wicked awesome example of 'int to string' (and string to int) converstions.

Definately gotta check it out yo.

i think my main problem here is getting the compiler to arrange the 4 digit number into descending order and then storing that string into a character... after i do that, i'll be gravy... SOMEONE HELP!!! I CAN'T FIND ANYTHING ANYWHERE ON ARRANGING CHARACTERS WITHIN A STRING....

Woh. That IS a really wicked example, I was expecting itoa() or something.

bcianfrocca:
I remember another post like this one. But since you've shown some work this time, I'll try and help.

I see you've got the number in string form already, so you can proceed to sort the individual digits in the string, which is the part you're having trouble on I'm assuming. It looks like you're trying to sort the string by a swapping method (bubble sort? Can't think of the name), but here's an easier method you can use:
1) Create a second string.
2) Find the lowest digit in the original string (converted from the int).
3) Copy the digit to the first position in the second string.
4) Find the next lowest digit in the original string.
5) Copy this digit to the next position in the second string.
6) Repeat 4 and 5 until you have the entire string sorted in lowest to highest order.

Since you know the number of digits there are, you can just do a (nested) for loop instead of playing with tricky 'valid' control variables. One for loop just controls the number of digits you copy into the second string, and another loop inside of it helps you to find the lowest number in the original string.

Hope this helps! :)

I change some statements, when input '1234', output is '2341',
not correct, how to decrease 'if' code?

Code:

---

#include <iostream>
#include <stdlib.h>
#include <iomanip>
#include <cstring>
using namespace std;

int main()
{
bool valid = false;
char initialdigit [5];
int x;
int tmp;
int firstinteger;

 cout<<"Please enter a non-zero 4 digit number..."<<endl;
 cin>> initialdigit;

 firstinteger = atoi (initialdigit);

 if (firstinteger > 0)
    valid = true;

 while (valid)
    {
    if (initialdigit [0] < initialdigit [1])
      {
        tmp = initialdigit [0];
        initialdigit [0] = initialdigit [1];
        initialdigit [1] = tmp;
        }
    if (initialdigit [1] < initialdigit [2])
        {
          tmp = initialdigit [1];
          initialdigit [1] = initialdigit [2];
          initialdigit [2] = tmp;
        }
    if (initialdigit [2] < initialdigit [3])
      {
          tmp = initialdigit [2];
          initialdigit [2] = initialdigit [3];
          initialdigit [3] = tmp;
        }

       
    valid = false;
    }

//cout<<firstinteger<<endl;
cout<<initialdigit [0]<<initialdigit [1]
    <<initialdigit [2]<<initialdigit [3]<<endl;

      system("PAUSE");
      return 0;
}

---

Sorting is very easy to do:

Code:

---

#include <algorithm>
#include <functional>
...
//Sort first 4 characters of initialdigit array in descending order
std::sort(initialdigit,initialdigit+4,std::greater<char>());

---

BTW, the stdlib.h header is deprecated, the new version of that header is cstdlib

toysoldier: if you want to learn what's wrong with your code review what happens with the while() loop. Since valid is assigned false after the first time through the loop, the loop will stop after sorting just the first value. You need to keep going after the first element is sorted somehow. To use the swap technique like you have it, probably the easiest way is to use two loops that are nested. The outer loop will keep track of how many times to do a series of comparisons. The inner loop will keep track of which comparison you are doing. The ifs can be reduced to just one comparison that is an abstract comparison rather than a hard coded comparison like you use. In general, this technique is called a basic bubble sort. There are lots of variations that can be used to optimize the basic version, so develop/use one that you can understand. There are a number of posts about bubble sorts on the board and I'm sure you can find lots of references by "googling" as well.

Of course, as hk_mp5kpdw idicated, you can always use the generic sort from the STL algorhithm header file if this isn't some form of homework and you just want something that works whether you understand it or not.

I think It may help you:
- There are a big difference between number and number in character.
- There are a big difference between string terminated by zero and a character.
:rolleyes:

Code:

---

//sort number
//mybe algorithm is Bubble Sort
//a bruce force algorithm
//optimized for check input buffer
#include <iostream>
using namespace std;
//convert from a character to a number
int chartoint(char c)
        {
                char buffer[2];
                buffer[1]=0;//string need to be terminated by ZERO
                buffer[0]=c;
                return atoi(buffer);
        }
//use to swap
void c_swap(char &a, char &b)
        {
                char buffer;
                buffer=a;
                a=b;
                b=buffer;
        }
//check "number" is number or not
bool checknumberstring(char*s)
        {

                int l = strlen(s);
                for (int i=0; i<l+1;i++)
                                if (s[i]<'0' && s[i]>'9')
                                        return false;
                return true;
        }
//main here

#define        NUMBER        10

int main()

        {
        char initialdigit [NUMBER];
        unsigned int firstinteger;
        cout<<"Please enter a non-zero digit number..."<<endl;
        fgets(initialdigit, NUMBER, stdin);

// check input data here

        if (strlen(initialdigit)!=NUMBER-1 || checknumberstring(initialdigit)==false)
                {
                        cout << "Error! Input..." << endl;
                        system("PAUSE");
                        return 1;
                }
        firstinteger = atoi (initialdigit);
        if (firstinteger > 0)
                {
                for (int i=0; i<NUMBER-1; i++)
                        for (int j=0; j<NUMBER-1; j++)
                                if (chartoint(initialdigit [j]) < chartoint(initialdigit [j+1]))
                                        c_swap(initialdigit [j], initialdigit [j+1]);
                }
        cout<<initialdigit<<endl;
        system("PAUSE");
        return 0;
        }

---

well use 'sstream' would be a easy way.