HDU-6194 string string string(後綴自動機)

HDU-6194 string string string(後綴自動機)

這個題用後綴自動機作真的簡單

統計一下每一個狀態\(|endpos|\)是否等於\(k\)就能獲得答案

#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);
    }
}