P3181 [HAOI2016]找相同字符

P3181 [HAOI2016]找相同字符

对一个串建SAM，另一个串在这上面跑，到达一点时，假设经过了\(cnt\)个点
计算这个串所有后缀产生的贡献就好了，直接暴力跑上去可能会超时，topsort预处理一下

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<queue>
using namespace std;
typedef long long LL;
const LL maxn=500000;
LL nod,last,n,T;
LL len[maxn],fail[maxn],son[maxn][26],Ans[maxn],sum[maxn],c[maxn],p[maxn],size[maxn],fval[maxn];
char s[maxn];
inline void Insert(LL c){
	LL np=++nod,p=last;
	len[np]=len[p]+1;
	last=np;
	while(p&&!son[p][c]){
		son[p][c]=np,
		p=fail[p];
	}
	if(!p)
	    fail[np]=1;
	else{
		LL q=son[p][c];
		if(len[q]==len[p]+1)
		    fail[np]=q;
		else{
			LL nq=++nod;
			len[nq]=len[p]+1;
			fail[nq]=fail[q];
			memcpy(son[nq],son[q],sizeof(son[q]));
			fail[np]=fail[q]=nq;
			while(p&&son[p][c]==q){
				son[p][c]=nq,
				p=fail[p];
			}
		}
	}
	size[last]=1;
}
int main(){	
	nod=last=1;
	scanf("%s",s);
	LL Len=strlen(s);
	for(LL i=0;i<Len;++i)
		Insert(s[i]-'a');
		
	for(LL i=1;i<=nod;++i)
	    c[len[i]]++;
    for(LL i=1;i<=nod;++i)
	    c[i]+=c[i-1];
    for(LL i=1;i<=nod;++i)
	    p[c[len[i]]--]=i;
	for(LL i=nod;i>=1;--i)
        size[fail[p[i]]]+=size[p[i]];
    for(LL i=1;i<=nod;i++)
	    fval[p[i]]=(len[p[i]]-len[fail[p[i]]])*size[p[i]]+fval[fail[p[i]]];
        
	scanf("%s",s);
	LL now=1,cnt=0,ans=0;
	Len=strlen(s);
	for(LL i=0;i<Len;++i){
		LL c=s[i]-'a';
		if(son[now][c])
		    ++cnt,
		    now=son[now][c];
		else{
			while(now&&!son[now][c])
			    now=fail[now];
			if(!now)
				cnt=0,
			    now=1;
			else
			    cnt=len[now]+1,
			    now=son[now][c];
		}
		if(now!=1)
		    ans+=fval[fail[now]]+(cnt-len[fail[now]])*size[now];
	}
	printf("%lld",ans);
	return 0;
}/*
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*/