additional data structures
public static boolean isUniqueChars(String str) {
long checker1 = 0;
long checker2 = 0;
long checker3 = 0;
long checker4 = 0;
for (int i = 0; i < str.length(); ++i) {
int val = str.charAt(i);
int toCheck = val / 64;
val %= 64;
switch (toCheck) {
case 0:
if ((checker1 & (1L << val)) > 0) {
return false;
}
checker1 |= (1L << val);
break;
case 1:
if ((checker2 & (1L << val)) > 0) {
return false;
}
checker2 |= (1L << val);
break;
case 2:
if ((checker3 & (1L << val)) > 0) {
return false;
}
checker3 |= (1L << val);
break;
case 3:
if ((checker4 & (1L << val)) > 0) {
return false;
}
checker4 |= (1L << val);
break;
}
}
return true;
}