牛客 - All with Pairs

传送门：牛客 - All with Pairs

思路分析

先把每一个后缀的hash值存起来，然后枚举$s[i]$的每一个前缀，记录有多少个后缀能够匹配，但是不能直接计算贡献，因为同一个字符串可能匹配到多个前缀，所以要进行去重
比如 $aba$就会同时计算$a$和$aba$，实际上只取最长的那个，可以通过next数组进行去重，$cnt[next[i]]-=cnt[i]$

AC代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) (x).size()
#define lowbit(x) (x)&(-x)
#define all(x) (x).begin(),(x).end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace FastIO {
#define BUF_SIZE 100000
#define OUT_SIZE 100000
    bool IOerror=0;
    inline char nc() {
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if(p1==pend) {
            p1=buf;
            pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if(pend==p1) {
                IOerror=1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';
    }
    template<class T> inline bool read(T &x) {
        bool sign=0;
        char ch=nc();
        x=0;
        for(; blank(ch); ch=nc());
        if(IOerror)return false;
        if(ch=='-')sign=1,ch=nc();
        for(; ch>='0'&&ch<='9'; ch=nc())x=x*10+ch-'0';
        if(sign)x=-x;
        return true;
    }
    template<class T,class... U>bool read(T& h,U&... t) {
        return read(h)&&read(t...);
    }
#undef OUT_SIZE
#undef BUF_SIZE
};
using namespace std;
using namespace FastIO;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int INF = 0x3f3f3f3f;
const int N = 1e6+10;
const int P = 998244353;
const ll base = 1331;

typedef unsigned long long ull;

int nex[N];
map<ull,int>cnt;
ll sum[N];
string s[N];

void ins(string x) {
    ull hash=0,ba=1;
    int len=sz(x);
    for(int i=len-1; i>=0; i--) {
        hash=x[i]*ba + hash;
        ba=ba*base;
        cnt[hash]++;
    }
}

void getnext(string x) {
    int j=nex[0]=-1;
    int len=sz(x);
    for(int i=1; i<len; i++) {
        while(j>-1 && x[i]!=x[j+1]) j=nex[j];
        if(x[i]==x[j+1]) j++;
        nex[i]=j;
    }
}


signed main() {

#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    int n;
    cin>>n;
    for(int i=1; i<=n; i++) {
        cin>>s[i];
        ins(s[i]);
    }
    ll ans=0;
    for(int i=1; i<=n; i++) {
        getnext(s[i]);
        ull hash=0;
        int len=s[i].size();
        
        for(int j=0; j<len; j++) {
            hash=hash*base+s[i][j];
            sum[j]=cnt[hash];
        }
        for(int j=0; j<len; j++) {
            if(nex[j]==-1) continue;
            sum[nex[j]]-=sum[j];
        }
        
        for(int j=0; j<len; j++) ans=(ans + 1LL*sum[j]*(j+1)*(j+1)%P) %P;
    }
    cout<<ans<<endl;




    return 0;
}