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#define ALPHABET_SIZE 26
struct SuffixAutomaton {
struct State {
int length; int link; int next[ALPHABET_SIZE];
State() { memset(next, 0, sizeof(next)); }
};
static const int MAX_N = 100000; // Maximale Länge des Strings.
State states[2 * MAX_N];
int size, last;
SuffixAutomaton(string &s) { // Laufzeit: O(|s|)
size = 1; last = 0;
states[0].length = 0;
states[0].link = -1;
for (auto c : s) extend(c);
}
void extend(char c) { // Werte von c müssen bei 0 beginnen.
c -= 'a';
int current = size++;
states[current].length = states[last].length + 1;
int pos = last;
while (pos != -1 && !states[pos].next[(int)c]) {
states[pos].next[(int)c] = current;
pos = states[pos].link;
}
if (pos == -1) states[current].link = 0;
else {
int q = states[pos].next[(int)c];
if (states[pos].length + 1 == states[q].length) {
states[current].link = q;
} else {
int clone = size++;
states[clone].length = states[pos].length + 1;
states[clone].link = states[q].link;
memcpy(states[clone].next, states[q].next,
sizeof(states[q].next));
while (pos != -1 && states[pos].next[(int)c] == q) {
states[pos].next[(int)c] = clone;
pos = states[pos].link;
}
states[q].link = states[current].link = clone;
}}
last = current;
}
// Paar mit Startposition und Länge des LCS. Index in Parameter s.
ii longestCommonSubstring(string &s) { // Laufzeit: O(|s|)
int v = 0, l = 0, best = 0, bestpos = 0;
for (int i = 0; i < (int)s.size(); i++) {
int c = s[i] - 'a';
while (v && !states[v].next[c]) {
v = states[v].link;
l = states[v].length;
}
if (states[v].next[c]) { v = states[v].next[c]; l++; }
if (l > best) { best = l; bestpos = i; }
}
return ii(bestpos - best + 1, best);
}
};
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