Thread: Arrays

I have to make an array that follows the criteria below. It reads in the numbers from the numbers in quotes below. The dark green are the scores I want to read in from the array, the blue is the max contestants and the red is the max judges. My array kept failing and crashing the output window.

A. An array to store all the contestant’s scores.
i. type int
ii. should be 2 dimensional, of size MAX_CONTESTANTS x MAX_JUDGES
iii. index [i][j] should store contestant i’s score from judge j. (contestant and judge
numbers start from 0)

3
2 4 10
85 90 100 98
78 82 47 77
3 5 12
85 90 100 98 76
78 82 47 77 75
94 6 97 98 99
2 3 15
80 20 50
78 22 53

Practical programming includes a lot of common sense problem solving, and this is an example.

Post up your attempt to solve this, and let's see where you went awry. You should be able to figure it out, but maybe the in's and out's of allocating the array is the problem.

But let's see what's the problem.

I couldnt get the 2 d array to work however I did get it to read in the numbers and print them in the output correctly using a while loop and 1 d array

Code:

int main() {
    
    int num_shows, num_contestants, num_judges, sd_threshold;
    double average;
    
    // Open the text file.
    FILE* ifp = fopen("ucfidol.txt", "r");
    
    //scanning info from text file
    fscanf(ifp, "%d", &num_shows);
    fscanf(ifp, "%d%d%d", &num_contestants, &num_judges, &sd_threshold);
    
    //declaring array size by text file
    int score[num_contestants][num_judges];
    int i, j;
    
    //populates 2d array with numbers from text file
    for (i=0; i<num_contestants+1; i++) 
      for (j=0; j<num_judges; j++)
        fscanf(ifp, "%d", &score[i][j]);

Why is it "num_contestants+1" in the "i" array but "num_judges" in the "j" array?

Originally Posted by dubbin240

I couldnt get the 2 d array to work.

After you populate the 2d array with values what happens? Does the array have any values?

Hunter

That was a typo...it should be judge in the i array and contestants in the j..the way the file reads in...and when I run it shows a blank output window then says it has stopped working

Do you mind posting your input file and your entire main function. That'll make it easier to find the problem.

Hunter

Code:

#include <stdio.h>
#include <math.h>


int main() {
    
    int num_shows, num_contestants, num_judges, sd_threshold;
    double average;
    
    // Open the text file.
    FILE* ifp = fopen("ucfidol.txt", "r");
    
    //scanning info from text file
    fscanf(ifp, "%d", &num_shows);
    fscanf(ifp, "%d%d%d", &num_contestants, &num_judges, &sd_threshold);
    
    //declaring array size by text file
    int score[num_contestants][num_judges];
    int i, j;
    
    //populates 2d array with numbers from text file
    for (i=0; i<num_judges; i++) {
      for (j=0; j<num_contestants; j++)
        fscanf(ifp, "%d", &score[i][j]);
         printf("%d",score[i][j]);
        //printf("%d",score[num_c]);      //testing the file input
        printf(" "); 
  }
       

    
   
    // Close the file.
    fclose(ifp);
    
        system("PAUSE");
    return 0;
}

Attachment 10432

okay so I found the problem, now it's time for you to find it

I would look at how you declare your array:

Code:

int score[num_contestants][num_judges];

Then look at the order of variables inside your for loops:

Code:

for (i=0; i<num_judges; i++) {
      for (j=0; j<num_contestants; j++)
        fscanf(ifp, "%d", &score[i][j]);
         printf("%d",score[i][j]);
        //printf("%d",score[num_c]);      //testing the file input
        printf(" "); 
  }

Also use braces after every for loop, it will make your issue easier to see.

Hope that helps,
Hunter

I don't think you can declare a 2-d array dynamically sized like that.

sure you can:
the initial size of the array is set to the bounds passed in for num_contestests and num_judges, and the array is filled with zeros.

Hunter

okay so I found the problem, now it's time for you to find it

Ok so when you say you figured it out you actually ran it and it worked? I changed the int score to have judges for i and contestants for j...I also rearranged some of the variables several times and still didn't run properly

I ran it and it worked how you described it in your previous post. But is judges supposed to be for i? Look at your array declaration.

O ok yea it should be contestants...I'm just not really familiar with arrays and I don't really get how it reads in or stores the numbers

Google a C array tutorial on the net, and bone up on the subject. It's critical to understand it, before you can work with them.