can't figure out a loop...

i finally crunched this program out... sorry for all the confusion, i'm new to C++ and am anxious to learn... the program below works fine but i need it to repeat a certain section if they enter a number that's not 4 digits long... i have it to say "Must be 4 digit number." but then it kicks out of the program, i know it's because of the "system(pause)" thing, but i have that in there only until i get the loop to work... i want it to keep asking them for a 4 digit num. until they enter a 4 dig. number.... thanks guys...

Code:

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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <process.h>
#include <ctype.h>
#include <iostream.h>

char initial[5];    //declaration of variables and character string
int initialint, i, x, y, num;

void swap(int a, int b); // function prototypes for swapping/sorting.
void sort_des();
void sort_asc();

void main()
{

        cout<<"Please enter a 4 digit non-zero number..."<<" ";  //gets initial value
        cin>>initial;
        initialint=strlen(initial);
        if(initialint!=4)          //checks to see if number is 4 digits in length
        {
                cout<<"Must be a 4 digit number."<<endl;
        system("pause");
        }

        for(i=0; i<4; i++)
        {
                if(!isdigit(initial[i]))  //makes sure it is only digits and not letters or characters or something
                {
                        cout<<"Must be numbers only."<<endl;
                        system("pause");
                }
        }

        while(strcmp(initial, "6174")!=0)  //checks to see if it is 6174 or not
        {
                cout<<""<<endl;
                sort_des();                //prints out the new numbers of the desc. and asc. strings
                x=atoi(initial);
                cout<<"  "<<initial<<endl;
                sort_asc();
                y=atoi(initial);
                cout<<"- "<<initial<<endl;

                if(x==y)      // this is to exempt the '9999, 8888, etc.' or zero
                {
                        cout<<"Does not apply..."<<endl;
                        break;
                }

                num=x-y;  // subtraction for descending and ascending
                sprintf(initial, "%4d", num);
                cout<<"------"<<endl;
                cout<<"  "<<initial<<endl;

        cout<<""<<endl;    // repeated this section of code to double up the "6174" at the end like on the homework paper.
                sort_des();
                x=atoi(initial);
                cout<<"  "<<initial<<endl;
                sort_asc();
                y=atoi(initial);
                cout<<"- "<<initial<<endl;

                if(x==y)
                {
                        cout<<"Does not apply..."<<endl;
                        break;
                }

                num=x-y;
                sprintf(initial, "%4d", num);
                cout<<"------"<<endl;
                cout<<"  "<<initial<<endl;
        }

        cout<<""<<endl;
        system("pause");
}



void swap(int a, int b)  // function definition for swapping characters in the string
{
char t;

        t=initial[a];
        initial[a]=initial[b];
        initial[b]=t;
}

void sort_des()        //function definition for sorting characters into descending order
{
int s, f;

        for(s=0; s<initialint-1; s++)
        {
                for(f=s+1; f<initialint; f++)
                {
                        if(initial[f]>initial[s]) swap(f, s);
                }
        }
}

void sort_asc()        //function definition for sorting characters into ascending order
{
int s, f;

        for(s=0; s<initialint-1; s++)
        {
                for(f=s+1; f<initialint; f++)
                {
                        if(initial[f]<initial[s]) swap(f, s);
                }
        }
}

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i know the loop needs to be right around in here, but i'm not certain how to do it...

Code:

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if(initialint!=4)          //checks to see if number is 4 digits in length
        {
                cout<<"Must be a 4 digit number."<<endl;
        system("pause");
        }

---

while(initialint!=4) should work instead of if(initialint!=4)

Code:

---

do           
{             
    cout<<"Please enter a 4 digit non-zero number..."<<" ";           
    cin>>initial;
}while(initial.size() != 4);

---

I think that will work

deepfrye: didn't work...

what didnt work about it?

This will work:

Code:

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do           
{             
    cout<<"Please enter a 4 digit non-zero number..."<<" ";           
    cin>>initial;
}while(strlen(initial) != 4 || atoi(initial) == 0);

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thanks, i appreciate it!

You don't see my reply, man?
All ready complete, man.
+Not limit number inputed.
+Check number or char
+Check size of number

I've completed everything for you, man.

Read carefully before post again, man.

:rolleyes:

Code:

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//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;
        }
////////////////////////////////////////////////////////////
#define        NUMBER        10
////////////////////////////////////////////////////////////
//main here//
////////////////////////////////////////////////////////////
int main()
        {
        char initialdigit [NUMBER];
        unsigned int firstinteger;
////////////////////////////////////////////////////////////
        cout<<"Please enter a non-zero digit number..."<<endl;
        fgets(initialdigit, NUMBER, stdin);
////////////////////////////////////////////////////////////
        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;
        }
////////////////////////////////////////////////////////////

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