Problem understandnig...pls help

This is a discussion on Problem understandnig...pls help within the C++ Programming forums, part of the General Programming Boards category; hi everyone, can someone help me explain no what is this code means? Code: bool FindNumber(int iPos) { int iNumberTwo, ...

  1. #1
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    Nov 2005
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    Problem understandnig...pls help

    hi everyone, can someone help me explain no what is this code means?

    Code:
    bool FindNumber(int iPos)
    {
        int iNumberTwo, iTotal;
    
        if(iPos < 1)
        
        return false;
        if (iPos == number)
        {
            iTotal = array[iPos-1] + array[0];
            if (IsPrime(iTotal))
            { 
                for(int j=0; j< number; j++)
                {
                    printf("%d ", array[j]);
                }
                printf("\n");
                return true;
            }
            else
            return false;
        }
        
        iNumberTwo = GetNumber(iPos, 0);
        while(iNumberTwo != 0)
        {
            array[iPos] = iNumberTwo;
            iTotal = array[iPos]+array[iPos-1];
            if (IsPrime(iTotal))
            {
    //   printf("Now in %d, try %d, and %d is prime\n", iPos, ring[iPos], iTotal);
    //   for(int i=0; iĦq =iPos; i++)
    //   printf("%d ", ring[i]);
    //   printf("\n\n");
                if (FindNumber(iPos+1) == true)
                {
    // iPos --
                }      
            }
            iNumberTwo = GetNumber(iPos, iNumberTwo);
        }
        return false;
    }

  2. #2
    Hardware Engineer
    Join Date
    Sep 2001
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    1,398
    You don't understand ANY of it???? Take a look at the tutorials, especially the tutorials covering if-statments, loops, and functions.

    I could comment every line... but I don't have the time right now. And, it's going to be hard to understand if you don't already know what an array is, or what a function is.

    It's a single function, not a complete program. It calls at least two other functions which are not defined here: IsPrime() and GetNumber().

    Also, printf() is unusual in C++. (It's a C function.)

  3. #3
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    ok thank you for replying, i understand those. and this is the whole program...

    Code:
    // Problem A: Prime Ring
    
    #include <stdio.h>
    #include <iostream>
    #include <cstdlib>
    #include <math.h>
    using namespace std;
    
    bool NotInRing(int iPos, int iNum);
    int GetNumber(int iPos, int iNumber);
    bool IsPrime(int iNum);
    bool FindNumber(int iPos);
    
    int ring[16];
    int m;
    
    int main()
    {
        int  i, j, k;
    //  insert the 1 value into first position which is ring[0]
        ring[0] = 1;
    
        while (scanf("%d", &m))
        {
            if (m == 0)
            break;
    
    //  printf("Get %d\n", m);
            if (FindNumber(1) == true)
            {
                for(j=0; j<m; j++)
                {
                    printf("%d ", ring[j]);
                }
                printf("\n");
            }
        }// end while.
        system("pause");
        return 0;
    }
    
    bool NotInRing(int iPos, int iNum)
    {
        for(int i=0; i<iPos; i++)
        {
            if (iNum == ring[i])
            {
                return false;
            }
        }
        return true;
    }
    
    int GetNumber(int iPos, int iNumber)
    {
        for(int i=iNumber+1; i<=m; i++)
        {
            if (NotInRing(iPos, i))
            return i;
        }
        return 0;  
    }
    
    bool IsPrime(int iNum)
    {
        for (int i=2; i<=sqrt((double)iNum); i++) //sqr/sqrt 
        {
            if (iNum == ((int)iNum/i)*i)		// (inum%i == 0)
            return false;
        }
        return true;
    }
    
    
    bool FindNumber(int iPos)
    {
        int iNumberTwo, iTotal;
        
        if(iPos < 1)
        
        return false;
    
        if (iPos == m)
        {
            iTotal = ring[iPos-1] + ring[0];
            if (IsPrime(iTotal))
            {
                for(int j=0; j< m; j++)
                {
                    printf("%d ", ring[j]);
                }
                printf("\n");
                return true;
            }
            else
            return false;
        }
        
        iNumberTwo = GetNumber(iPos, 0);
        while(iNumberTwo != 0)
        {
            ring[iPos] = iNumberTwo;
            iTotal = ring[iPos]+ring[iPos-1];
            if (IsPrime(iTotal))
            {
    //   printf("Now in %d, try %d, and %d is prime\n", iPos, ring[iPos], iTotal);
    //   for(int i=0; iĦq =iPos; i++)
    //   printf("%d ", ring[i]);
    //   printf("\n\n");
                if (FindNumber(iPos+1) == true)
                {
    // iPos --;
                }      
            }
            iNumberTwo = GetNumber(iPos, iNumberTwo);
        }
        return false;
    }
    this program works perfect for me , and this is exactly what i want but wat do you mean printf() is for c?

    if it is for c, and what is in c++?

    thank you.

  4. #4
    Dae
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    printf for C, cout for C++. scanf for C, cin for C++. math.h for C, cmath for C++. Like said, check out the tutorials on this site.

    As for the program, I'm not sure exactly what it does, and I'm not sure I'd spend the time doing so. Glancing over it I'd guess it allows you to add numbers to a global array, search the array for numbers, and check if its a prime number. See this is what commenting on the programs use, and functions use, etc. is good for.
    Warning: Have doubt in anything I post.

    GCC 4.5, Boost 1.40, Code::Blocks 8.02, Ubuntu 9.10 010001000110000101100101

  5. #5
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    actually i already work it out. but still need to thank you for all who participate and helps.

    what is this code mean which is in the FindNumber function?

    Code:
     if(iPos < 1)
        
        return false;
        if (iPos == number)

  6. #6
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    by wat i think for the IPOS, i think is i position...
    well that is just wat i guess..

    not really sure....

  7. #7
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    That's a check for valid input. The function expects iPos (passed in by the function's caller) to be >= 1. If it's not, the function bails out rather than running with bad data.

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