A logic error in my program

This is a discussion on A logic error in my program within the C Programming forums, part of the General Programming Boards category; Code: /*To find out the value in the array that the sum of all elements of the same number is ...

  1. #1
    Registered User
    Join Date
    Sep 2012
    Posts
    7

    A logic error in my program

    Code:
    /*To find out the value in the array that the sum of all elements of the same number is the largest*/
    /* Can anyone tell me what the logic error is? Thanks. */
    int findMaxValue(int arr[], int n){ //n = number of elements in array
        int ans=0;
        int maxValue = 0;
        int temp[80]; //maximum of array lenth is 80
        int i,j;
        
        for(i=0; i<n; i++){
            for(j=1; j<100; j++){ //the value in array is from 0 to 100
                if(arr[i] ==  j)
                    temp[j] += j;
            }
        }
        for (j=1; j<100; j++){
            if(temp[j] > maxValue){
                maxValue = temp[j];
                ans = j;
            }
        }
        return ans;
    }
    //Thank you.

  2. #2
    Registered User
    Join Date
    Sep 2006
    Posts
    8,868
    Welcome to the forum, 20120903!

    So if the array had:

    7 three's, 3 sixes, and 2 ten's, you want the program to calculate that it's the 7 three's that have the greatest value, right?

    I don't see logic for that. Maybe:

    in an array, count up how many of each number, you have:
    Code:
    for(i=0;i<n;i++)
       array[array[i]]++;
    Which just tells you you have X number of three's, and Y number of four's, etc. (Obviously, this is bogus unless the array[] values are set to zero, first!!

    Now go back through the array values you just calculated, and figure out the max. In pseudo code:

    Code:
    int max = 0;
    for(each number in the array) {
       multiply the value in the array, by i
       if the result is > max
          max = result
    }
    There are other ways to do this, but this is what I'd suggest.

  3. #3
    Algorithm Dissector iMalc's Avatar
    Join Date
    Dec 2005
    Location
    New Zealand
    Posts
    6,304
    In your last loop j goes up to 99, but you use that to index into the array called 'temp' which only contains 80 items. That's called a buffer overrun.
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

  4. #4
    Registered User
    Join Date
    Sep 2012
    Posts
    7
    Thank you for both of your suggestion.
    Let's take 7 three's, 3 sixes, and 2 ten's to explain my code.
    In the first loop, we can get temp[3]=21, temp[6]=18 and tmp[10]=10 as result.
    In the second loop, we obtain maxValue = 21 and the answer should be 3.
    I don't know why I can't get the correct result.

  5. #5
    Registered User
    Join Date
    May 2012
    Posts
    1,066
    Quote Originally Posted by 20120903 View Post
    I don't know why I can't get the correct result.
    You don't initialise your temp array thus it contains random values from INT_MIN to INT_MAX (these are the lower and upper limits for an integer on your computer). It's very likely that any element has a higher value than 21 and that's why you get the wrong index.

    You should change temp to
    Code:
    int temp[100] = { 0 };
    so that every element is set to 0.

    Bye, Andreas

  6. #6
    Registered User
    Join Date
    Sep 2012
    Posts
    7
    My code works now. Thank you.

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Error in logic
    By Mentallic in forum C Programming
    Replies: 2
    Last Post: 03-28-2010, 08:02 AM
  2. Error in logic
    By mesmer in forum C Programming
    Replies: 2
    Last Post: 10-21-2008, 06:42 AM
  3. C Program logic error?
    By bigmac(rexdale) in forum C Programming
    Replies: 27
    Last Post: 02-15-2008, 10:20 AM
  4. Logic Error...
    By Blackroot in forum C++ Programming
    Replies: 6
    Last Post: 01-28-2006, 05:21 AM
  5. logic error I think
    By sscook69 in forum C++ Programming
    Replies: 1
    Last Post: 04-26-2002, 10:08 PM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21