【BZOJ #4556】【Tjoi2016&Heoi2016】—字符串（后缀自动机+线段树合并）

传送门

仍然和后缀数组做法一样考虑二分
由于是公共前缀
对反串建$Sam$

然后倍增找到$C,C+mid$对应的那个节点
就相当于看$endpos$是否有在$a,b-mid+1$里
线段树合并维护$endpos即可

#include<bits/stdc++.h>
using namespace std;
const int RLEN=1<<20|1;
inline char gc(){
    static char ibuf[RLEN],*ib,*ob;
    (ob==ib)&&(ob=(ib=ibuf)+fread(ibuf,1,RLEN,stdin));
    return (ob==ib)?EOF:*ib++;
}
#define gc getchar
inline int read(){
    char ch=gc();
    int res=0,f=1;
    while(!isdigit(ch))f^=ch=='-',ch=gc();
    while(isdigit(ch))res=(res+(res<<2)<<1)+(ch^48),ch=gc();
    return f?res:-res;
}
#define ll long long
#define re register
#define pii pair<int,int>
#define pic pair<int,char>
#define fi first
#define se second
#define pb push_back
#define cs const
#define bg begin
#define poly vector<int>
#define chemx(a,b) ((a)<(b)?(a)=(b):0)
#define chemn(a,b) ((a)>(b)?(a)=(b):0)
cs int N=100005;
int n,m;
namespace Seg{
	cs int M=N*50;
	int lc[M],rc[M],siz[M],tot;
	#define mid ((l+r)>>1)
	inline void insert(int &u,int l,int r,int p){
		u=++tot;siz[u]++;
		if(l==r)return;
		if(p<=mid)insert(lc[u],l,mid,p);
		else insert(rc[u],mid+1,r,p);
	}
	inline void merge(int &u,int r1,int r2){
		if(!r1||!r2){u=r1+r2;return;}
		u=++tot,siz[u]=siz[r1]+siz[r2];
		merge(lc[u],lc[r1],lc[r2]);
		merge(rc[u],rc[r1],rc[r2]);
	}
	inline int query(int u,int l,int r,int st,int des){
		if(!u)return 0;
		if(st<=l&&r<=des)return siz[u];
		int res=0;
		if(st<=mid)res+=query(lc[u],l,mid,st,des);
		if(mid<des)res+=query(rc[u],mid+1,r,st,des);
		return res;
	}
	#undef mid
}
namespace Sam{
	cs int M=N<<1;
	int nxt[M][26],fa[M],len[M],pos[M],rt[M],tot,last,ed[M];
	inline void init(){
		tot=last=1;
	}
	inline void insert(int c,int id){
		int cur=++tot,p=last;
		pos[cur]=id,ed[id]=cur;
		last=cur,len[cur]=len[p]+1;
		for(;p&&!nxt[p][c];p=fa[p])nxt[p][c]=cur;
		if(!p)fa[cur]=1;
		else{
			int q=nxt[p][c];
			if(len[p]==len[q]-1)fa[cur]=q;
			else{
				int clo=++tot;
				len[clo]=len[p]+1,fa[clo]=fa[q];
				memcpy(nxt[clo],nxt[q],sizeof(nxt[q]));
				for(;p&&nxt[p][c]==q;p=fa[p])nxt[p][c]=clo;
				fa[cur]=fa[q]=clo;
			}
		}
	}
	int buc[M],rk[M];
	vector<int> e[M];
	int f[M][20];
	void dfs(int u){
		for(int i=1;i<=18;i++)f[u][i]=f[f[u][i-1]][i-1];
		for(int &v:e[u]){
			f[v][0]=u,dfs(v);
		}
	}
	inline void build(){
		for(int i=1;i<=tot;i++)buc[len[i]]++;
		for(int i=1;i<=tot;i++)buc[i]+=buc[i-1];
		for(int i=1;i<=tot;i++)rk[buc[len[i]]--]=i;
		for(int i=tot;i>=1;i--){
			int u=rk[i];
			if(pos[u])Seg::insert(rt[u],1,n,pos[u]);
			Seg::merge(rt[fa[u]],rt[fa[u]],rt[u]);
		}
		for(int i=2;i<=tot;i++)e[fa[i]].pb(i);
		dfs(1);
	}
	inline bool check(int l,int a,int b,int c,int d){
		int u=ed[c];
		for(int i=18;~i;i--)if(len[f[u][i]]>=l)u=f[u][i];
		return Seg::query(rt[u],1,n,a,b-l+1)>0;
	}
	inline int query(int a,int b,int c,int d){
		int l=1,r=min(d-c+1,b-a+1),res=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(check(mid,a,b,c,d))l=mid+1,res=mid;
			else r=mid-1;
		}
		return res;
	}
}
char s[N];
int main(){
	n=read(),m=read();
	Sam::init();
	scanf("%s",s+1);
	for(int i=n;i;i--)Sam::insert(s[i]-'a',i);
	Sam::build();
	for(int i=1;i<=m;i++){
		int a=read(),b=read(),c=read(),d=read();
		cout<<Sam::query(a,b,c,d)<<'
';
	}
}