Getting runtime error in C in spoj toandfro classical

Question

Here is the link to the problem. http://www.spoj.com/problems/TOANDFRO/ And here is the link to my code http://ideone.com/w5wafl On codepad,it says floating point exception. Here is link to codepad http://codepad.org/FW9bKp5k (remove the space bw code--pad) why is it giving runtime error. is it because of error in strings or array. I am putting the code here.

#include <stdio.h>
#include <string.h>

int main(void) 
{
    int width_of_array, length_of_array, i,j , k;
    k = 0;
    char input_array[300], answer[300][300];

    scanf("%d", &width_of_array);
    scanf("%s", input_array);

    length_of_array = strlen(input_array) / width_of_array;
    for (i = 0 ; i < length_of_array ; i++)
     {
        if (i % 2 == 0)
         {  
            for ( j = 0 ; j < width_of_array ; j++)
              {
                answer[i][j] = input_array[k++];
              }
         }
        else
         {
            for (j = width_of_array - 1 ; j >= 0 ; j--)
              {
                answer[i][j] = input_array[k++];
              }
         }
    }
    for (j = 0 ; j < width_of_array ; j++)
     {
        for (i = 0 ; i < length_of_array ; i++)
         {
            printf("%c", answer[i][j]);
         }
     }
    return 0;
}

You never check `scanf()`'s return value, the value of `width_of_array` might be `0` or anything, there is no way to know unless you confirm that `scanf()` returned `1`. — Iharob Al Asimi, Dec 19 '15 at 17:47
In any of your test you don't give any input and expect output . How is that going to give you correct result without behaving wired ? — ameyCU, Dec 19 '15 at 17:50
@iharob Sorry.My fault. Feeling like an idiot now. am a bit new to competitive programming. Should have checked before. — Vishal_ranjan, Dec 19 '15 at 17:54

score 1 · Accepted Answer · answered Dec 19 '15 at 17:58

1

The line length_of_array = strlen(input_array) / width_of_array; will be a division by zero if the user inputs zero as the width of the array. CodePad flags this as a floating point error, but at runtime it results in undefined behavior.

answered Dec 19 '15 at 17:58

Dylan Kirkby

1,427
11
19

Thanks for pointing out. It would have been another possiblity, but it was mentioned that values are greater than zero,so this was not the problem.Anyways, Thanks!! – Vishal_ranjan Dec 20 '15 at 18:33

Getting runtime error in C in spoj toandfro classical

1 Answers1