P3181 [HAOI2016]找相同字符

水题 建两个自动机跑转移就行了

#include<bits/stdc++.h>
#define rep(i,a,n) for(int i=a;i<=n;++i)
#define per(i,a,n) for(int i=n;i>=a;--i)
#define pb push_back
#define fi first
#define se second
#define io std::ios::sync_with_stdio(false)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int P = 1e9+7, INF = 0x3f3f3f3f;

ll gcd(ll a,ll b)
{
    return b?gcd(b,a%b):a;
}
ll qpow(ll a,ll n)
{
    ll r=1%P;
    for (a%=P; n; a=a*a%P,n>>=1)if(n&1)r=r*a%P;
    return r;
}
const int maxn=3*2e5;

struct Suffix_Automata {
  int maxlen[maxn], trans[maxn][26], link[maxn], Size, Last;
  int siz[maxn];
  int t[maxn],A[maxn];
  Suffix_Automata() { Size = Last = 1; }
  inline void Extend(int id) {
    int cur = (++ Size), p;
    siz[Size]=1;
    maxlen[cur] = maxlen[Last] + 1;
    for (p = Last; p && !trans[p][id]; p = link[p]) trans[p][id] = cur;
    if (!p) link[cur] = 1;
    else {
      int q = trans[p][id];
      if (maxlen[q] == maxlen[p] + 1) link[cur] = q;
      else {
        int clone = (++ Size);
        maxlen[clone] = maxlen[p] + 1;
        memcpy(trans[clone], trans[q],sizeof(trans[q]));
        link[clone] = link[q];
        for (; p && trans[p][id] == q; p = link[p]) trans[p][id] = clone;
        link[cur] = link[q] = clone;
      }
    }
    Last = cur;
  }
  void buildtree()
  {
      for(int i=1;i<=Size;i++) t[maxlen[i]]++;
      for(int i=1;i<=Size;i++) t[i]+=t[i-1];
      for(int i=1;i<=Size;i++) A[t[maxlen[i]]--]=i;
      for(int i=Size;i>=1;i--)
      {   int now=A[i];
          int fa=link[now];
          siz[fa]+=siz[now];
      }
  }
} T1,T2;
char a[200005];
char b[200005];
ll ans;
void dfs(int cura,int curb)
{
    for(int i=0;i<26;i++)
    {
        if(T1.trans[cura][i]&&T2.trans[curb][i])
        {
            ans+=1ll*T1.siz[T1.trans[cura][i]]*T2.siz[T2.trans[curb][i]];
            dfs(T1.trans[cura][i],T2.trans[curb][i]);
        }
    }
}
int main()
{
     cin>>a+1;
     cin>>b+1;
     int n=strlen(a+1);
     for(int i=1;i<=n;i++)
     {
       T1.Extend(a[i]-'a');
     }
     n=strlen(b+1);
     for(int i=1;i<=n;i++)
        T2.Extend(b[i]-'a');
     T1.buildtree();T2.buildtree();
     dfs(1,1);
     cout<<ans<<endl;

}