Question about Recursive Functions

This is a discussion on Question about Recursive Functions within the C++ Programming forums, part of the General Programming Boards category; Show the exact screen-output of each of the following programs: c) Code: #include <stdio.h> int f (int a) { if ...

  1. #1
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    Question about Recursive Functions

    Show the exact screen-output of each of the following programs:

    c)

    Code:
    #include <stdio.h>
    int f (int a)
    {
    if (a== 1)
    return 1;
    else if (a==2)
    return 3;
    else 
    return (f(a-1) + f(a-2));
    } //end of function
    void main ()
    {
    int n;
    printf ("Enter n:\n");
    scanf ("%d", &n);
    printf("%d", f(n));
    }
    Hint: Assume entered value of n = 6


    answer:18
    ===========================================


    Code:
    #include<stdio.h>
    
     
    
    int myfunction(int p, int q)
    
    {
    
    if (p == q)
    
    return p;
    
    else if (p < q)
    
    return myfunction(q - p, p);
    
    else
    
    return myfunction(p - q, q);
    
    }
    
     
    
    void main()
    
    {
    
    int result;
    
    result=myfunction(20,4);
    
    printf("%d",result);
    
    }
    answer:4




    my question is how to get the answer????

  2. #2
    and the hat of wrongness Salem's Avatar
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    > void main ()
    main returns an int - see the FAQ

    Also learn how to indent code with some consistency. All this "to the left" indentation is much too difficult to follow.

    > my question is how to get the answer?
    You mean other than running it?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  3. #3
    Registered User hk_mp5kpdw's Avatar
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    Quote Originally Posted by jack999
    Show the exact screen-output of each of the following programs:

    c)

    Code:
    #include <stdio.h>
    int f (int a)
    {
    if (a== 1)
    return 1;
    else if (a==2)
    return 3;
    else 
    return (f(a-1) + f(a-2));
    } //end of function
    void main ()
    {
    int n;
    printf ("Enter n:\n");
    scanf ("%d", &n);
    printf("%d", f(n));
    }
    Hint: Assume entered value of n = 6


    answer:18
    Code:
    f(6) = 
    f(5)                             + f(4) = 
    f(4)               + f(3)        + f(3)        + f(2) =
    f(3)        + f(2) + f(2) + f(1) + f(2) + f(1) +   3 =
    f(2) + f(1) +   3  +   3  +   1  +   3  +   1  +   3 = 
      3  +   1  +   3  +   3  +   1  +   3  +   1  +   3 =
    
    
    
    18
    See if you can answer the other one now.
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  4. #4
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    Code:
    f(6) = 
    f(5)                             + f(4) = 
    f(4)               + f(3)        + f(3)        + f(2) =
    f(3)        + f(2) + f(2) + f(1) + f(2) + f(1) +   3 =
    f(2) + f(1) +   3  +   3  +   1  +   3  +   1  +   3 = 
      3  +   1  +   3  +   3  +   1  +   3  +   1  +   3 =
    i didnot get it

  5. #5
    Registered User hk_mp5kpdw's Avatar
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    Sigh... after I put all that effort into aligning my post.

    Do you at least understand the following?

    1. f(6) = f(5) + f(4)
    2. f(5) = f(4) + f(3)
    3. f(4) = f(3) + f(2)
    4. f(3) = f(2) + f(1)
    5. f(2) = 3
    6. f(1) = 1

    If you can understand all of those, then it is simply a matter of substitution. If you can't...
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  6. #6
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    Code:
    1. f(6) = f(5) + f(4)
    2. f(5) = f(4) + f(3)
    3. f(4) = f(3) + f(2)
    4. f(3) = f(2) + f(1)
    5. f(2) = 3
    6. f(1) = 1
    i got it
    thanks

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