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| package main
type dfa struct {
tran [][128]int
accept []bool
}
type dfa_state struct {
states []*nfa_state
hash int
i int
accept bool
}
type nfa_edge struct {
next *nfa_state
epsilion bool
ch byte
}
type nfa_state struct {
edges []*nfa_edge
i int
accept bool
}
func (s *nfa_state) add_e(next *nfa_state) {
s.edges = append(s.edges, &nfa_edge{epsilion: true, next: next})
}
func (s *nfa_state) add_char(c byte, next *nfa_state) {
s.edges = append(s.edges, &nfa_edge{ch: c, next: next})
}
type nfa struct {
start *nfa_state
end *nfa_state
}
func nfa_e() *nfa {
start := &nfa_state{}
end := &nfa_state{}
start.add_e(end)
return &nfa{start, end}
}
func nfa_char(c byte) *nfa {
start := &nfa_state{}
end := &nfa_state{}
start.add_char(c, end)
return &nfa{start, end}
}
func nfa_cat(a *nfa, b *nfa) *nfa {
*a.end = *b.start
return &nfa{a.start, b.end}
}
func nfa_or(a *nfa, b *nfa) *nfa {
start := &nfa_state{}
end := &nfa_state{}
start.add_e(a.start)
a.end.add_e(end)
start.add_e(b.start)
b.end.add_e(end)
return &nfa{start, end}
}
func nfa_star(a *nfa) *nfa {
start := &nfa_state{}
end := &nfa_state{}
start.add_e(a.start)
start.add_e(end)
a.end.add_e(end)
a.end.add_e(a.start)
return &nfa{start, end}
}
func nfa_alloc_id(n *nfa_state, id int) int {
if n.i != 0 {
return id
}
n.i = id
id++
for _, e := range n.edges {
id = nfa_alloc_id(e.next, id)
}
return id
}
func nfa_move(states []*nfa_state, c byte) []*nfa_state {
set := make(map[*nfa_state]struct{})
for _, st := range states {
for _, e := range st.edges {
if !e.epsilion && e.ch == c {
set[e.next] = struct{}{}
}
}
}
next := make([]*nfa_state, 0, len(set))
for k, _ := range set {
next = append(next, k)
}
return next
}
func e_closure(t []*nfa_state) *dfa_state {
stack := make([]*nfa_state, len(t))
set := make(map[*nfa_state]struct{}, len(t))
for i := 0; i < len(t); i++ {
set[t[i]] = struct{}{}
stack[i] = t[i]
}
for len(stack) > 0 {
t := stack[len(stack)-1]
stack = stack[:len(stack)-1]
for _, e := range t.edges {
if !e.epsilion {
continue
}
if _, ok := set[e.next]; !ok {
set[e.next] = struct{}{}
stack = append(stack, e.next)
}
}
}
hash := 0
ec := []*nfa_state{}
accept := false
for st, _ := range set {
if !accept {
accept = st.accept
}
ec = append(ec, st)
hash += st.i
for i := len(ec) - 2; i >= 0; i-- {
if ec[i].i <= st.i {
break
}
t := ec[i+1]
ec[i+1] = ec[i]
ec[i] = t
}
}
return &dfa_state{hash: hash, states: ec, accept: accept}
}
func in_states(states []*dfa_state, u *dfa_state) int {
for i, st := range states {
if u.hash != st.hash || len(u.states) != len(st.states) {
continue
}
diff := false
for j := 0; j < len(u.states); j++ {
if u.states[j] != st.states[j] {
diff = true
break
}
}
if !diff {
return i
}
}
return -1
}
func nfa_to_dfa(n *nfa) *dfa {
dstates := []*dfa_state{e_closure([]*nfa_state{n.start})}
dtran := make([][128]int, 1)
daccept := []bool{false}
stack := []int{0}
for len(stack) > 0 {
t := dstates[stack[len(stack)-1]]
stack = stack[:len(stack)-1]
charset := [128]bool{}
for _, st := range t.states {
for _, e := range st.edges {
if e.epsilion {
continue
}
charset[e.ch] = true
}
}
for a := range charset {
if !charset[a] {
continue
}
u := e_closure(nfa_move(t.states, byte(a)))
i := in_states(dstates, u)
if i == -1 {
u.i = len(dstates)
dstates = append(dstates, u)
dtran = append(dtran, [128]int{})
daccept = append(daccept, u.accept)
stack = append(stack, u.i)
} else {
u = dstates[i]
}
dtran[t.i][a] = u.i
}
}
return &dfa{tran: dtran, accept: daccept}
}
|