blob: 8b7982245de4290885b7982b1781292d8bce7804 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
constexpr int ALPHABET_SIZE = 26;
constexpr char OFFSET = 'a';
struct SuffixAutomaton {
struct State {
int len, link = -1;
int nxt[ALPHABET_SIZE] = {}; // map if large Alphabet
State(int l) : len(l) {}
};
vector<State> st{0};
int last = 0;
SuffixAutomaton(const string &s) {
st.reserve(2 * sz(s));
for (auto c : s) extend(c - OFFSET);
}
void extend(int c) {
st.emplace_back(st[last].len + 1);
int p = last, cur = last = sz(st) - 1;
for (; p != -1 && !st[p].nxt[c]; p = st[p].link) {
st[p].nxt[c] = cur;
}
if (p == -1) st[cur].link = 0;
else {
int q = st[p].nxt[c];
if (st[p].len + 1 == st[q].len) {
st[cur].link = q;
} else {
st.emplace_back(st[p].len + 1);
st.back().link = st[q].link;
copy(all(st[q].nxt), st.back().nxt); // back.nxt=[q].nxt
for (; p != -1 && st[p].nxt[c] == q; p = st[p].link) {
st[p].nxt[c] = sz(st) - 1;
}
st[q].link = st[cur].link = sz(st) - 1;
}}
}
vector<int> calculateTerminals() {
vector<int> terminals;
for (int p = last; p != -1; p = st[p].link) {
terminals.push_back(p);
}
return terminals;
}
// Pair with start index (in t) and length of LCS.
pair<int, int> longestCommonSubstring(const string &t) {
int v = 0, l = 0, best = 0, bestpos = 0;
for (int i = 0; i < sz(t); i++) {
int c = t[i] - OFFSET;
for (; v && !st[v].nxt[c]; v = st[v].link) l = st[v].len;
if (st[v].nxt[c]) v = st[v].nxt[c], l++;
if (l > best) best = l, bestpos = i;
}
return {bestpos - best + 1, best};
}
};
|
