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  #1  
Old 19-Mar-2008, 22:59
Sabreen Khan Sabreen Khan is offline
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Recursion function

I am having a lot of problem with recursive functions which i'v recently started learning.
The problem: The user gives 2 int inputs, eg 1 and 1. The output should b a series like this 1 1 2 3 5 8 13 21 34 ...till 50
i.e the next number is the sum of the previous 2 numbers.Recursive functions are a bit confusing and since i am a beginner, i would be glad if you could help me.
  #2  
Old 20-Mar-2008, 00:21
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WaltP WaltP is offline
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Re: Recursion function

Sure, we'd be glad to help. But this isn't the Psychic Programmer's Forum. unless you show us what you've done and explained what the problem is, we're at a loss to help.

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  #3  
Old 20-Mar-2008, 01:37
Sabreen Khan Sabreen Khan is offline
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Re: Recursion function

CPP / C++ / C Code:
#include<stdio.h>
#include<conio.h>
 
int sum;
int rec(int previous,int result,int sum)
{
    if (result<50)
    {
    sum= result+previous;
    previous=result;
    result=sum;
    return(result);
    rec(previous,result,sum);    
 
    }
 
}
 
main()
{ 
    int previous=0;
    int result=1;
    //rec(previous,result,sum);
    int z;
    z=rec(previous,result,sum);
    printf("%d",z);
}
Code:
Compiling...
recursive function.c
E:\AIUB NOTES\PROGRAMMING LANGUAGE\recursive function.c(49) : warning C4715: 'rec' : not all control paths return a value
 
recursive function.obj - 0 error(s), 1 warning(s)

The output gives 1. Whereas i should be getting : 11235813...............till less than 50
Last edited by admin II : 20-Mar-2008 at 05:20. Reason: Please surround your C code with [cpp] your code [/cpp]
  #4  
Old 20-Mar-2008, 01:38
Sabreen Khan Sabreen Khan is offline
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Re: Recursion function

I feel that i have probably placed the printf in the wrong place,or there has been some problem with the allignment of the codes. I dont understand what i have done wrong. Please help me if you can. it would be very kind of you.
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Old 21-Mar-2008, 20:00
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Re: Recursion function

No, it's because when you call rec() the first time, you return and the program ends. You never get a second call to rec().

Execute the code you have by hand. Then rethink your logic in the function.
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Old 21-Mar-2008, 23:56
Sabreen Khan Sabreen Khan is offline
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Re: Recursion function

hey, Waltp...Im stuck. Please help me out. Even if i place return after calling rec() it gives the same output.
  #7  
Old 23-Mar-2008, 21:49
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Re: Recursion function

And what did you come up with when you did your re-think? Did you follow your code as I suggested? What happened? What did you find out?
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  #8  
Old 24-Mar-2008, 11:51
Sabreen Khan Sabreen Khan is offline
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Re: Recursion function

CPP / C++ / C Code:
#include<stdio.h>
#include<conio.h>
 
 
 
int rec(int previous,int result)
{
    int sum;
    if (result<50) 
    {
    sum= result+previous;
    previous=result;
    result=sum;
    printf("%d ",result);
    rec(previous,result);    
}
    return;
 
}
 
main()
{ 
    int previous=0;
    int result=1;
    rec(previous,result);
 
}



i finally came up with this and it works...thanku anyways..
Last edited by admin II : 24-Mar-2008 at 11:57. Reason: Please surround your C code with [cpp] your code [/cpp]
  #9  
Old 29-Mar-2008, 15:34
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Re: Recursion function

check it out


CPP / C++ / C Code:
#include<iostream.h>
#include<conio.h>
 
long Fibonacci(int); // function declaration //
 
 
void main()
{
clrscr();
int fib;
 
cout<<"Enter The Limit To Find The Fibonacci Series=";
    cin>>fib;
 
for (int i=0;i<fib;i++) // to display first 10 fibonacci numbers//
    cout << Fibonacci(i) << " ";
 
    getch();
 
}
 
 
long Fibonacci(int num) // function calling //
{
if (num == 0)
    return 0;
if (num == 1)
    return 1;
return Fibonacci(num-1) + Fibonacci(num-2); // use of recursion //
}
Last edited by admin II : 29-Mar-2008 at 16:42. Reason: Please surround your C++ code with [cpp] your code [/cpp]
  #10  
Old 31-Mar-2008, 09:22
faisalnet5 faisalnet5 is offline
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Re: Recursion function

Dude...Sabreen....u r basically working with a very common problem in Computer Science.....it is called "Fibonacci series". Just Google it up....see the algorithm for that series...try to understand it, try to get the meaning of recursive functions....thats it....U will be the one then...

Good Luck
 
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