HDU-6194 string string string(后缀自动机)

HDU-6194 string string string(后缀自动机)

这个题用后缀自动机做真的简单

统计一下每个状态\(|endpos|\)是否等于\(k\)就能得到答案

#include<bits/stdc++.h>
using namespace std;

#define reg register
typedef long long ll;
#define rep(i,a,b) for(int i=a,i##end=b;i<=i##end;++i)
#define drep(i,a,b) for(int i=a,i##end=b;i>=i##end;--i)

#define pb push_back
template <class T> inline void cmin(T &a,T b){ ((a>b)&&(a=b)); }
template <class T> inline void cmax(T &a,T b){ ((a<b)&&(a=b)); }

char IO;
template<class T=int> T rd(){
	T s=0;
	int f=0;
	while(!isdigit(IO=getchar())) if(IO=='-') f=1;
	do s=(s<<1)+(s<<3)+(IO^'0');
	while(isdigit(IO=getchar()));
	return f?-s:s;
}

const int N=2e5+10;


int n,k;
char s[N];
int trans[N][26],link[N],stcnt,len[N],lst,sz[N];

struct Edge{
	int to,nxt;
}e[N];
int head[N],ecnt;
void AddEdge(int u,int v) {
	e[++ecnt]=(Edge){v,head[u]};
	head[u]=ecnt;
}

void Init(){
	link[0]=-1,len[0]=0;
	rep(i,0,stcnt) {
		head[i]=0,sz[i]=0;
		rep(j,0,25) trans[i][j]=0;
	}
	stcnt=lst=ecnt=0;
}

void Extend(int c) {
	int cur=++stcnt,p=lst;
	len[cur]=len[lst]+1,sz[cur]=1;
	while(~p && !trans[p][c]) trans[p][c]=cur,p=link[p];
	if(p==-1) link[cur]=0;
	else {
		int q=trans[p][c];
		if(len[q]==len[p]+1) link[cur]=q;
		else {
			int clone=++stcnt;
			memcpy(trans[clone],trans[q],104);
			link[clone]=link[q];
			len[clone]=len[p]+1;
			while(~p && trans[p][c]==q) trans[p][c]=clone,p=link[p];
			link[cur]=link[q]=clone;
		}
	}
	lst=cur;
}

ll ans;
void dfs(int u) {
	for(reg int i=head[u];i;i=e[i].nxt) {
		int v=e[i].to;
		dfs(v);
		sz[u]+=sz[v];
	}
	if(u &&	sz[u]==k) ans+=max(0,len[u]-len[link[u]]);
}

int main(){
	rep(kase,1,rd()){ 
		k=rd();scanf("%s",s+1),n=strlen(s+1);
		Init();
		rep(i,1,n) Extend(s[i]-'a');
		rep(i,1,stcnt) AddEdge(link[i],i);
		ans=0,dfs(0),printf("%lld\n",ans);
	}
}