spelling-bee-regex.js

var dfa = DFA.create();
var i, j;
for (i = 0; i <= 5; i++) for (j = 0; j <= 1; j++) {
	dfa.addState(i + "." + j);
}

for (i = 0; i <= 5; i++) for (j = 0; j <= 1; j++) {
	dfa.addTransition(i + "." + j, Math.min(5, i+1) + "." + Math.min(j+1, 1), C('c'));
	dfa.addTransition(i + "." + j, Math.min(5, i+1) + "." + j, A(C('f'), C('a'), C('e'), C('t'), C('i'), C('o')));
}

for (i = 0; i <= 5; i++) for (j = 0; j <= 1; j++) {
	var s = i + "." + j;
	if (s != "0.0" && s != "5.1") dfa.eliminateState(s);
}

var regex = L(
	S(dfa.transitionRegex("0.0", "0.0")),
	dfa.transitionRegex("0.0", "5.1"),
	S(dfa.transitionRegex("5.1", "5.1")),
);

console.log("^(" + regex.simplify().toString(false) + ")$");