字符串哈希模板

bool isprime(int n) {
    if (n <= 1) {
        return false;
    }
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}
int findPrime(int n) {
    while (!isprime(n)) {
        n++;
    }
    return n;
}

void slove(){
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    const int P = findPrime(rng() % 900000000 + 100000005);

    string s;
    cin>>s;
    int n=s.size();
    s='.'+s;

    vector<int> h(n + 3,0), p(n + 3,0);
    p[0]=1;
    for(int i=1;i<=n;i++){
        p[i]=p[i-1]*10LL%P;
        //预处理过程
        h[i]=(h[i-1]*10LL+s[i]-'a')%P;
        //计算字符串的哈希值
    }

    auto get = [&](int l, int r) {
        return (h[r]+1LL*(P-h[l-1])*p[r-l+1])%P;    
    };
}