spoj1812 Longest Common Substring II( 后缀自动机 )

贴个代码...

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#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

const int maxn = 200009;

const int cn = 26;

struct Node {

Node *fa, *ch[cn];

int len, Min, Max;

void upd() {

Min = min(Min, Max);

}

} pool[maxn], *pt, *root, *last;

void upd(Node* &t, int &v) {

t->Max = max(t->Max, v);

}

Node* newNode(int v) {

pt->fa = NULL;

pt->len = v;

memset(pt->ch, 0, sizeof pt->ch);

return pt++;

}

void SAM_init() {

pt = pool;

root = last = newNode(0);

}

void Extend(int c) {

Node *p = last, *np = newNode(p->len + 1);

for(; p && !p->ch[c]; p = p->fa)

p->ch[c] = np;

if(!p)

np->fa = root;

else {

Node* q = p->ch[c];

if(p->len + 1 == q->len)

np->fa = q;

else {

Node* nq = newNode(p->len + 1);

memcpy(nq->ch, q->ch, sizeof q->ch);

nq->fa = q->fa;

q->fa = np->fa = nq;

for(; p && p->ch[c] == q; p = p->fa)

p->ch[c] = nq;

}

}

last = np;

}

char s[maxn];

void SAM_build() {

scanf("%s", s);

for(int i = 0, n = strlen(s); i < n; i++)

Extend(s[i] - ‘a‘);

}

bool work() {

if(scanf("%s", s) == -1)

return false;

for(Node* t = root; t != pt; t++)

t->Max = 0;

int n = strlen(s);

Node* t = root;

for(int i = 0, lth = 0; i < n; i++) {

int c = s[i] - ‘a‘;

if(t->ch[c])

upd(t = t->ch[c], ++lth);

else {

for(; t && !t->ch[c]; t = t->fa);

if(!t)

t = root, lth = 0;

else

lth = t->len + 1, upd(t = t->ch[c], lth);

}

}

for(Node* o = pt; --o != pool; )

upd(o->fa, o->Max);

for(Node* o = pt; --o; ) {

o->upd();

if(o == pool) break;

}

return true;

}

int main() {

SAM_init();

SAM_build();

for(Node* t = root; t != pt; t++)

t->Min = t->len;

while(work());

int ans = 0;

for(Node* t = root; t != pt; t++)

ans = max(ans, t->Min);

printf("%d\n", ans);

return 0;

}

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