/**
* Constructs sub-automaton corresponding to decimal numbers of value at most x.substring(n) and
* length x.substring(n).length().
*/
private static State atMost(String x, int n) {
State s = new State();
if (x.length() == n) s.setAccept(true);
else {
char c = x.charAt(n);
s.addTransition(new Transition(c, atMost(x, (char) n + 1)));
if (c > '0') s.addTransition(new Transition('0', (char) (c - 1), anyOfRightLength(x, n + 1)));
}
return s;
}
/**
* Constructs sub-automaton corresponding to decimal numbers of value at least x.substring(n) and
* length x.substring(n).length().
*/
private static State atLeast(String x, int n, Collection<State> initials, boolean zeros) {
State s = new State();
if (x.length() == n) s.setAccept(true);
else {
if (zeros) initials.add(s);
char c = x.charAt(n);
s.addTransition(new Transition(c, atLeast(x, n + 1, initials, zeros && c == '0')));
if (c < '9') s.addTransition(new Transition((char) (c + 1), '9', anyOfRightLength(x, n + 1)));
}
return s;
}
/**
* Constructs sub-automaton corresponding to decimal numbers of value between x.substring(n) and
* y.substring(n) and of length x.substring(n).length() (which must be equal to
* y.substring(n).length()).
*/
private static State between(
String x, String y, int n, Collection<State> initials, boolean zeros) {
State s = new State();
if (x.length() == n) s.setAccept(true);
else {
if (zeros) initials.add(s);
char cx = x.charAt(n);
char cy = y.charAt(n);
if (cx == cy)
s.addTransition(new Transition(cx, between(x, y, n + 1, initials, zeros && cx == '0')));
else { // cx<cy
s.addTransition(new Transition(cx, atLeast(x, n + 1, initials, zeros && cx == '0')));
s.addTransition(new Transition(cy, atMost(y, n + 1)));
if (cx + 1 < cy)
s.addTransition(
new Transition((char) (cx + 1), (char) (cy - 1), anyOfRightLength(x, n + 1)));
}
}
return s;
}
/**
* Constructs sub-automaton corresponding to decimal numbers of length x.substring(n).length().
*/
private static State anyOfRightLength(String x, int n) {
State s = new State();
if (x.length() == n) s.setAccept(true);
else s.addTransition(new Transition('0', '9', anyOfRightLength(x, n + 1)));
return s;
}