#include <stdio.h>
#include <string.h>
int validateStudentNumber(char* studentNumber) {
int prefixes[5] = {19, 20, 21, 22, 23};
int length = strlen(studentNumber);
int isValid = 0;
// Checking for prefixes.
for (int i = 0; i < 5; i++) {
char prefix[3];
sprintf(prefix, "%02d", prefixes[i]);
if (strncmp(studentNumber, prefix, 2) == 0) {
isValid = 1;
break;
}
}
if (isValid && (length != 9 || strspn(studentNumber, "0123456789") != 9)) {
isValid = 0;
}
return isValid;
}
int main() {
char studentNumber[10];
printf("Enter the student number: ");
scanf("%s", studentNumber);
if (validateStudentNumber(studentNumber)) {
printf("Valid student number.\n");
} else {
printf("Invalid student number. Prefix does not match valid enrollment years.\n");
}
return 0;
}