Output of this program is not getting accepted - c

Question

I am trying to submit an answer given on codechef "https://www.codechef.com/problems/FLOW009"
this is my code.
#include <stdio.h>
int main()
{
int t, i;
scanf("%d",&t);
i=t;
float qty[t], per[t], sum[t];
do{
scanf("%f %f", &qty[t-1], &per[t-1]);
sum[t-1] = qty[t-1] * per[t-1];
if(qty[t-1] > 1000 )
{
sum[t-1] = sum[t-1] - (sum[t-1]*10)/100;
}
}while(--t);
do{
printf("%f\n", sum[i-1]);
}while(--i);
return 0;
}
It tells me again again that my solution is wrong and I am unable to understand it.I can't ask questions there as I have less karma.

Answer 1

Two things:
Never store values for each test cases until told as sometimes the test cases may be large ,in place calculate and print output for each test cases. This may save memory ,time and confusion.
What could be done with few lines why to do with too much code and mess.
See this:
#include <stdio.h>
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
int p,q;
scanf("%d %d",&q,&p);
float ans=(float)q*p;
if(q>1000)
ans-=(ans/10);
printf("%f\n",ans);
}
return 0;
}

Answer 2

You cannot scan an int as a string. The sscanf() funtion scans a string according to the specified format string. This code could use more error checking.
$ cat FLOW009.c
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv)
{
char aline[100];
int t;
int quantity;
int price;
FILE *fh = fopen("FLOW009.txt", "rt");
if (fh == NULL) {printf("open failed"); exit(1);}
if (fgets(aline, 80, fh) != NULL) {
sscanf(aline, "%d", &t);
if (t < 1 || t > 1000) {
printf("ERROR: Value of t, %d, is outside the range 1 to 1000\n", t);
exit(1);
}
while (fgets(aline, sizeof(aline), fh) != NULL) {
sscanf(aline, "%d %d", &quantity, &price);
if (quantity > 0 && price <= 100000) {
printf("%.6f\n", (float)quantity * (float)price);
} else {
printf("ERROR: Quantity and price are not within accepted limits.\n");
}
}
}
exit(0);
}