結果

問題 No.663 セルオートマトンの逆操作
ユーザー fine
提出日時 2020-05-20 02:27:09
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 2 ms / 2,000 ms
コード長 4,803 bytes
コンパイル時間 1,564 ms
コンパイル使用メモリ 171,256 KB
実行使用メモリ 6,824 KB
最終ジャッジ日時 2024-10-01 23:25:41
合計ジャッジ時間 2,578 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge5
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ファイルパターン 結果
other AC * 29
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 #
プレゼンテーションモードにする

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr char newl = '\n';
// https://noshi91.hatenablog.com/entry/2019/03/31/174006
template <std::uint_fast64_t Modulus>
struct ModInt {
    using u64 = std::uint_fast64_t;
    static constexpr u64 MOD = Modulus;
    u64 val;
    constexpr ModInt(const u64 x = 0) noexcept : val(x % MOD) {}
    constexpr ModInt operator+() const noexcept { return ModInt(*this); }
    constexpr ModInt operator-() const noexcept {
        ModInt res(*this);
        if (res.val != 0) res.val = MOD - res.val;
        return res;
    }
    constexpr bool operator==(const ModInt& rhs) const noexcept { return val == rhs.val; }
    constexpr bool operator!=(const ModInt& rhs) const noexcept { return val != rhs.val; }
    // prefix increment/decrement
    constexpr ModInt& operator++() noexcept { return *this += ModInt(1); }
    constexpr ModInt& operator--() noexcept { return *this -= ModInt(1); }
    // postfix increment/decrement
    constexpr ModInt& operator++(int) noexcept {
        ModInt tmp(*this);
        ++*this;
        return tmp;
    }
    constexpr ModInt& operator--(int) noexcept {
        ModInt tmp(*this);
        --*this;
        return tmp;
    }
    constexpr ModInt operator+(const ModInt& rhs) const noexcept {
        return ModInt(*this) += rhs;
    }
    constexpr ModInt operator-(const ModInt& rhs) const noexcept {
        return ModInt(*this) -= rhs;
    }
    constexpr ModInt operator*(const ModInt& rhs) const noexcept {
        return ModInt(*this) *= rhs;
    }
    constexpr ModInt operator/(const ModInt& rhs) const noexcept {
        return ModInt(*this) /= rhs;
    }
    constexpr ModInt& operator+=(const ModInt& rhs) noexcept {
        val += rhs.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr ModInt& operator-=(const ModInt& rhs) noexcept {
        if (val < rhs.val) val += MOD;
        val -= rhs.val;
        return *this;
    }
    constexpr ModInt& operator*=(const ModInt& rhs) noexcept {
        val = val * rhs.val % MOD;
        return *this;
    }
    // prime Modulus only
    constexpr ModInt& operator/=(const ModInt& rhs) noexcept {
        return *this *= rhs.inv();
    }
    // prime Modulus only
    constexpr ModInt inv() const noexcept {
        return pow(*this, MOD - 2);
    }
};
template<std::uint_fast64_t Modulus>
constexpr ModInt<Modulus> pow(ModInt<Modulus> x, std::uint_fast64_t n) {
    ModInt<Modulus> res(1);
    while (n) {
        if (n & 1) res *= x;
        x *= x;
        n >>= 1;
    }
    return res;
}
template<std::uint_fast64_t Modulus>
istream& operator>>(istream& is, ModInt<Modulus>& x) {
    std::uint_fast64_t val;
    is >> val;
    x = ModInt<Modulus>(val);
    return is;
}
template<std::uint_fast64_t Modulus>
ostream& operator<<(ostream& os, const ModInt<Modulus>& x) {
    return os << x.val;
}
using mint = ModInt<1000000007>;
int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<int> e(n);
    for (int i = 0; i < n; i++) {
        cin >> e[i];
    }
    
    array< array<mint, 4>, 4> dp{};
    for (int i = 0; i < 4; i++) {
        dp[i][i] = 1;
    }
    for (int i = 1; i < n - 1; i++) {
        array< array<mint, 4>, 4> ndp{};
        for (int j = 0; j < 4; j++) {
            for (int k = 0; k < 4; k++) {
                if (k == 0 || k == 2) {
                    int nex = e[i];
                    ndp[j][nex] += dp[j][k];
                } else if (k == 1) {
                    if (e[i] == 0) continue;
                    ndp[j][2] += dp[j][k];
                    ndp[j][3] += dp[j][k];
                } else if (k == 3) {
                    int nex = 3 - e[i];
                    ndp[j][nex] += dp[j][k];                    
                }
            }
        }
        dp = move(ndp);
    }
    mint ans = 0;
    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            int val;
            if (j == 0 || j == 2) {
                val = e.back();
            } else if (j == 1) {
                if (e.back() == 0) continue;
                val = (i >> 1);
            } else if (j == 3) {
                val = 1 - e.back();                
            }  
            if (val != (i >> 1)) continue;
            int k = ((j & 1) << 1) | (i >> 1);
            if (k == 0 || k == 2) {
                val = e.front();
            } else if (k == 1) {
                if (e.front() == 0) continue;
                val = (i & 1);
            } else if (k == 3) {
                val = 1 - e.front();                
            }                       
            if (val != (i & 1)) continue;
            ans += dp[i][j];
        }
    }
    cout << ans << newl;
    return 0;
}
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