【后缀自动机】 SPOJ LCS2

解法CLJ论文上有讲。。。

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 200005
#define maxm 100005
#define eps 1e-7
#define mod 1000000007
#define INF 0x3f3f3f3f
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R
#define pii pair<int, int>
#pragma comment(linker, "/STACK:16777216")
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
// head

struct node
{
	int len, nlcs, lcs;
	node *fa, *next[26];
}pool[maxn], *root, *last, *tp[maxn];
char s[maxn];
int c[maxn];
int tot;

node* newnode(int len)
{
	node *p = &pool[tot++];
	p->len = p->lcs = len, p->nlcs = 0, p->fa = 0;
	memset(p->next, 0, sizeof p->next);
	return p;
}

void init()
{
	tot = 0;
	root = newnode(0);
	last = root;
	memset(c, 0, sizeof c);
}

void add(int c)
{
	node *p = last, *np = newnode(p->len + 1);
	last = np;
	for(; p && !p->next[c]; p = p->fa) p->next[c] = np;
	if(!p) np->fa = root;
	else {
		node *q = p->next[c];
		if(p->len + 1 == q->len) np->fa = q;
		else {
			node *nq = newnode(p->len + 1);
			*nq = *q;
			nq->len = nq->lcs = p->len + 1;
			q->fa = np->fa = nq;
			for(; p && p->next[c] == q; p = p->fa) p->next[c] = nq;
		}
	}
}

void solve()
{
	node *p = root;
	int res = 0;
	for(int i = 0; s[i]; i++) {
		int c = s[i] - 'a';
		if(p->next[c]) {
			res++, p = p->next[c];
			p->nlcs = max(p->nlcs, res);
		}
		else {
			for(; p && !p->next[c]; p = p->fa);
			if(!p) res = 0, p = root;
			else {
				res = p->len + 1, p = p->next[c];
				p->nlcs = max(p->nlcs, res);
			}
		}
	}
	for(int i = tot - 1; i > 0; i--) {
		tp[i]->lcs = min(tp[i]->lcs, tp[i]->nlcs);
		tp[i]->fa->nlcs = max(tp[i]->fa->nlcs, tp[i]->nlcs);
		tp[i]->nlcs = 0;
	}
}

void read()
{
	scanf("%s", s);
	int len = strlen(s);
	for(int i = 0; s[i]; i++) add(s[i] - 'a');
	for(int i = 0; i < tot; i++) c[pool[i].len]++;
	for(int i = 1; i <= len; i++) c[i] += c[i-1];
	for(int i = 0; i < tot; i++) tp[--c[pool[i].len]] = &pool[i];
	while(scanf("%s", s)!=EOF) solve();
}

void work()
{
	int ans = 0;
	for(int i = 0; i < tot; i++) {
		node *p = &pool[i];
		ans = max(ans, p->lcs);
	}
	printf("%d\n", ans);
}

int main()
{
	init();
	read();
	work();
	
	return 0;
}