C Bug: Character Count

Question

Count the number of characters only if the characters are ('A', 'T', 'C', 'G'), else 'Invalid input'.
==========
Example_01
==========
Input: ATTCCGG
Output:
A
1
T
2
C
2
G
2
==========
Example_02
==========
Input: AKLTCG
Output: Invalid input
==========
I have the code above which runs for the count but does not tell whether it is an invalid case.
Code: https://code.sololearn.com/ca25A24A3A9A
==========
Probably, the else if statement in the function, count, went wrong. not sure...

Any help, would be highly appreciated... Thanks

Answer 1

I think your issue may have been with fgets and the that it adds the newline character to the buffer if it is read.

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

#define MAX_SIZE_STRING 1000

// Not sure if you are only allowed caps but this version will only account for CAP 'A', 'T', 'C', and 'G'
// Sticking with keeping your string at 999 characters plus the '\0'

int main(void){
int count_of_ATCG[4] = { 0 };

printf("Enter string to test:\n");
char test_string[MAX_SIZE_STRING];
fgets(test_string, MAX_SIZE_STRING, stdin);
/* fgets() reads in at most one less than size characters from stream
and stores them into the buffer pointed to by s. Reading stops after
an EOF or a newline. If a newline is read, it is stored into the buffer.
A terminating null byte ('\0') is stored after the last character in
the buffer.

Your possible issue is that the '\n' (newline) character was being read
*/

for(int i = 0; i < (strlen(test_string) - 1); i++){
switch(test_string[i]){
case 'A' :
count_of_ATCG[0]++;
break;
case 'T' :
count_of_ATCG[1]++;
break;
case 'C' :
count_of_ATCG[2]++;
break;
case 'G' :
count_of_ATCG[3]++;
break;
default:
printf("Invalid input\n");
return 0;
}
}

printf("A: %i\nT: %i\nC: %i\nG: %i\n", count_of_ATCG[0], count_of_ATCG[1], count_of_ATCG[2], count_of_ATCG[3]);
return 0;
}

Answer 2

THANKS FOR THE HELP