need correction

This is a discussion on need correction within the C Programming forums, part of the General Programming Boards category; Hi can anybody correct my code please? Code: /*Write an algorithm that gets a positive entire number N then displays ...

  1. #1
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    need correction

    Hi can anybody correct my code please?

    Code:
       
    /*Write an algorithm that gets a positive entire number N then displays all perfect numbers less or 
    equal to N.*/
    
      #include<stdio.h>
      int main (void){
       int i,n,sum_div,num;
       char ans;
       do{
       sum_div=0;
       printf("---------------\n");
       printf("Enter number:");
       scanf("%d", &n);
       printf("Perfect numbers in the range [1,%d]:", n);
       
    
       for(num=2;num<=n;num++){
       for(i=1;i<=num/2;i++){
        if(num%i==0)
        sum_div+=i;
    
       }
        if(sum_div==num)
        printf("%d ",num);
       }
       
        printf("\nContinue? <Y/N>:");
        scanf(" %c", &ans);}
        while(ans=='Y'||ans=='y');
        printf("Bye:>_n\n");
        return(0);
        }

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    sum_div needs to be initialized to 0 each time before you start adding to it.

  3. #3
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    i think the pblm is with the for loops. but how do i initialize that each time?

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Code:
    for(num=2;num<=n;num++){
       sum_div = 0;
       for(i=1;i<=num/2;i++){
        if(num%i==0)
        sum_div+=i;

  5. #5
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    ohh thank youuuuuuuuuuu (k)

  6. #6
    Banned master5001's Avatar
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    To be even more direct about the rareness of perfect numbers how about writing a function like this.

    Example:

    Code:
    #include <stdio.h>
    #include <ctype.h>
    Include those two so that you can have your printf() and scanf() functions. You also need toupper() from ctype.h

    Code:
    const static long unsigned long perfect_numbers[] = {6, 28, 496, 8128, 33550336, 8589869056, 137438691328};
    "But Matt, that doesn't seem like so many numbers!!! You are ruining my program."

    That list constitutes all of the perfect numbers your computer will be able to safely comprehend without using GMP or something.

    Code:
    int is_perfect(long unsigned long value)
    {
      size_t i;
    
      for(i = 0; i < sizeof(perfect_numbers)/sizeof(*perfect_numbers); ++i)
       if(value == perfect_numbers[i])
        return 1;
    
      return 0;
    }
    All this function does is compares an input value (as a 64-bit value) to the list of known perfect numbers.

    Code:
    int main(void)
    {
      unsigned int n, i = 0;
    
      while(toupper(i) != 'N')
      {
        do
        {
          fputs("> Please input a number: ", stdout);
        } while(scanf("&#37;d", &n) != 1);
    
        for(i = 0; i < n; ++i)
          if(is_perfect(i))
            printf("** %d is perfect!! **\n", i);
    
        fputs("> Continue? ", stdout);
        i = getchar();
      }
    }
    Make sense?
    Last edited by master5001; 10-24-2008 at 03:53 PM.

  7. #7
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    thank you master5001 it works now, tabstop found out i just had to initialize sum_div correctly. thanks yall.

  8. #8
    Banned master5001's Avatar
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    I know. I just think you should be aware of the fact that its slow to check every number to see if its perfect or not when there are soooooooooooooooooooooooooooo many numbers that are not perfect. We only know of 44 of them now. And with the aid of google I found a list of them.

    I changed the code to get rid of that warning for you

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