A puzzle in C:

This is a discussion on A puzzle in C: within the C Programming forums, part of the General Programming Boards category; Any solution of this prolbem: Code: #include<stdio.h> void change() { /* Write something in this function so that the output ...

  1. #1
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    Lightbulb A puzzle in C:

    Any solution of this prolbem:

    Code:
    #include<stdio.h>
    
    void change()
    {
    
    /* Write something in this function so that the output of printf in mainfunction should give 5 . Do not change the main function */
    
    }
    
    void main()
    {
          int i=5;
    
          change();
    
           i=10;
    
            printf("%d",i);
    }

  2. #2
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    Sure.
    Code:
    #include<stdio.h>
    
    void change()
    {
    #define printf i=5,printf
    }
    
    void main()
    {
    	int i=5;
    	
    	change();
    	
    	i=10;
    	
    	printf("%d",i);
    }
    If I did your homework for you, then you might pass your class without learning how to write a program like this. Then you might graduate and get your degree without learning how to write a program like this. You might become a professional programmer without knowing how to write a program like this. Someday you might work on a project with me without knowing how to write a program like this. Then I would have to do you serious bodily harm. - Jack Klein

  3. #3
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    Quote Originally Posted by pianorain
    Sure.
    Code:
    #include<stdio.h>
    
    void change()
    {
    #define printf i=5,printf
    }
    
    void main()
    {
    	int i=5;
    	
    	change();
    	
    	i=10;
    	
    	printf("%d",i);
    }
    Wow, would of never thought of that one. I guess that's one of those classic obfuscation tricks.

  4. #4
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    Only way I knew how to do it. I don't usually use #define's in obfuscation. I think it's kind of cheap.
    If I did your homework for you, then you might pass your class without learning how to write a program like this. Then you might graduate and get your degree without learning how to write a program like this. You might become a professional programmer without knowing how to write a program like this. Someday you might work on a project with me without knowing how to write a program like this. Then I would have to do you serious bodily harm. - Jack Klein

  5. #5
    ATH0 quzah's Avatar
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    Code:
    void change( void )
    {
        printf("5");
        fflush( stdout );
        exit( 0 );
    }
    :P


    Quzah.
    Hope is the first step on the road to disappointment.

  6. #6
    Magically delicious LuckY's Avatar
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    Your solution won't work, quzah, because the statement requires that the printf statment in main() will result in printing "5." Nice try though.

    Here's my thought, along the same lines as pianorain's:
    Code:
    #include <stdio.h>
    
    void change() {
    /* Write something in this function so that the output of printf
       in mainfunction should give 5 . Do not change the main function */
      #define printf(a, x) putchar('5')
    }
    
    int main() {
      int i = 5;
      change();
      i = 10;
      
      printf("%d",i);
      
      return 0;
    }

  7. #7
    ATH0 quzah's Avatar
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    I know. I was faking it. Hence the ':P'.


    Quzah.
    Hope is the first step on the road to disappointment.

  8. #8
    and the hat of int overfl Salem's Avatar
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    > Any solution of this prolbem:
    Yeah, find a better book or teacher.
    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.

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