how can i solve this should be keys (5 or 10 keys if possible 10) of both letters and numbers.
here (about 5 num 
bers and letters long)
here I want to make an nfc locker later
int keys[] = {"key1", "key2", "key3", "key4", "key5"};
byte count = sizeof(keys);
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
for (byte i=0; i <= sizeof(keys); i++){
Serial.println(i);
Serial.println(keys);
}
}
void loop() {
// put your main code here, to run repeatedly:
}