結果

問題 No.599 回文かい
コンテスト
ユーザー tokusakurai
提出日時 2020-09-05 22:01:12
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 146 ms / 4,000 ms
コード長 5,122 bytes
コンパイル時間 2,007 ms
コンパイル使用メモリ 200,732 KB
最終ジャッジ日時 2025-01-14 07:17:55
ジャッジサーバーID
（参考情報） 		judge5 / judge3
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ファイルパターン 結果
other AC * 22
権限があれば一括ダウンロードができます

ソースコード

diff # 

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const ll MOD = 1000000007;
//const ll MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const double pi = acos(-1.0);
const double EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

template<ll mod>
struct Mod_Int{
    ll x;

    Mod_Int() = default;

    Mod_Int(ll y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    Mod_Int &operator += (const Mod_Int &p){
        x = (x + p.x) % mod;
        return *this;
    }

    Mod_Int &operator -= (const Mod_Int &p){
        x = (x + mod - p.x) % mod;
        return *this;
    }

    Mod_Int &operator *= (const Mod_Int &p){
        x = (x * p.x) % mod;
        return *this;
    }

    Mod_Int &operator /= (const Mod_Int &p){
        *this *= p.inverse();
        return *this;
    }

    Mod_Int &operator ++ () {return *this += Mod_Int(1);}

    Mod_Int operator ++ (int){
        Mod_Int tmp = *this;
        ++*this;
        return tmp;
    }

    Mod_Int &operator -- () {return *this -= Mod_Int(1);}

    Mod_Int operator -- (int){
        Mod_Int tmp = *this;
        --*this;
        return tmp;
    }

    Mod_Int operator - () const {return Mod_Int(-x);}

    Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;}

    Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;}

    Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;}

    Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;}

    bool operator == (const Mod_Int &p) const {return x == p.x;}

    bool operator != (const Mod_Int &p) const {return x != p.x;}

    Mod_Int inverse() const {
        assert(*this != Mod_Int(0));
        return pow(mod-2);
    }

    Mod_Int pow(ll k) const{
        Mod_Int now = *this, ret = 1;
        while(k){
            if(k&1) ret *= now;
            now *= now, k >>= 1;
        }
        return ret;
    }

    friend ostream &operator << (ostream &os, const Mod_Int &p){
        return os << p.x;
    }

    friend istream &operator >> (istream &is, Mod_Int &p){
        ll a;
        is >> a;
        p = Mod_Int<mod>(a);
        return is;
    }
};

using mint = Mod_Int<MOD>;

struct Random_Number_Generator {
    mt19937 mt;

    Random_Number_Generator() : mt(chrono::steady_clock::now().time_since_epoch().count()) {}

    int operator () (int l, int r){
        uniform_int_distribution<int> dist(l, r-1);
        return dist(mt);
    }

    int operator () (int r){ 
        return (*this)(0, r);
    }
};

using ull = unsigned long long;

struct Rolling_Hash{
    const ull mod = (1ull<<61)-1;

    ull calc_mod(ull x){
        ull ret = (x>>61) + x&mod;
        return ret - (ret >= mod? mod : 0);
    }

    ull mul(ull x, ull y){
        x = calc_mod(x), y = calc_mod(y);
        ull x1 = x>>31, x2 = x&((1ull<<31)-1), y1 = y>>31, y2 = y&((1ull<<31)-1);
        ull z = x1*y2 + x2*y1, z1 = z>>30, z2 = z&((1ull<<30)-1);
        return calc_mod(x1*y1*2 + x2*y2 + z1 + (z2<<31));
    }

    ull pow(ull x, int n){
        ull ret = 1;
        while(n){
            if(n&1) ret = mul(ret, x);
            x = mul(x, x), n >>= 1;
        }
        return ret;
    }

    ull base;
    vector<ull> hashed, pw;

    void set_base(){
        Random_Number_Generator rnd;
        while(true){
            int k = rnd(inf);
            if(gcd(mod-1, k) != 1) continue;
            base = pow(3, k);
            if(base < 256) continue;
            break;
        }
    }

    Rolling_Hash(const string &s){
        set_base();
        int n = sz(s);
        hashed.resize(n+1), pw.resize(n+1);
        hashed[0] = 0, pw[0] = 1;
        rep(i, n){
            pw[i+1] = mul(pw[i], base);
            hashed[i+1] = mul(hashed[i], base) + s[i];
            if(hashed[i+1] >= mod) hashed[i+1] -= mod;
        }
    }

    ull query(int l, int r){
        ull ret = hashed[r] + mod - mul(hashed[l], pw[r-l]);
        return ret - (ret >= mod? mod : 0);
    }

    ull get_hash(const string &s){
        ull ret = 0;
        rep(i, sz(s)){
            ret = mul(ret, base) + s[i];
            if(ret >= mod) ret -= mod;
        }
        return ret;
    }
};

int main(){
    string S;
    cin >> S;
    int N = sz(S), n = N/2;
    Rolling_Hash rh(S);
    mint dp[n+1];
    fill(dp, dp+n+1, 0);
    dp[0] = 1;
    rep(i, n){
        rep2(j, 1, n-i){
            if(rh.query(i, i+j) == rh.query(N-i-j, N-i)) dp[i+j] += dp[i];
        }
    }
    mint ans = 0;
    rep(i, n+1) ans += dp[i];
    cout << ans << endl;
}
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