#1152483 (C++17) No.3117 Reversible Tile

• 問題: No.3117 Reversible Tile
• ユーザー: 👑 AngrySadEight
• 提出日時: 2026-03-15 09:37:44
• 言語: C++17 (gcc 15.2.0 + boost 1.89.0)
• 結果: AC
• 実行時間: 244 ms / 3,000 ms
• コード長: 4,569 bytes
• コンパイル時間: 5,432 ms
• コンパイル使用メモリ: 218,636 KB
• 実行使用メモリ: 52,608 KB
• 最終ジャッジ日時: 2026-03-15 09:37:59
• 合計ジャッジ時間: 14,540 ms
• ジャッジサーバーID （参考情報）: judge1_1 / judge3_1

ファイルパターン	結果
sample	AC * 3
other	AC * 24

ソースコード

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint998244353;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

struct Query{
    ll left;
    ll right;
    ll sign;
};

struct S{
    ll min_val;
    ll min_cnt;
};

S op(S a, S b){
    S new_s;
    new_s.min_val = min(a.min_val, b.min_val);
    new_s.min_cnt = 0;
    if (a.min_val == new_s.min_val){
        new_s.min_cnt += a.min_cnt;
    }
    if (b.min_val == new_s.min_val){
        new_s.min_cnt += b.min_cnt;
    }
    return new_s;
}

ll INF = 1000000000000023LL;

S e(){
    return S{INF, 0};
}

S mapping(ll f, S x){
    x.min_val += f;
    return x;
}

ll composition(ll f, ll g){
    return f + g;
}

ll id(){
    return 0LL;
}

int main() {
    ll N, M;
    cin >> N >> M;
    vector<ll> A(N);
    rep(i, N){
        cin >> A[i];
    }
    // 極大区間の個数
    vector<pll> rle;
    rle.push_back(make_pair(A[0], 1));
    for (ll i = 1; i < N; i++){
        if (rle.back().first == A[i]){
            rle[rle.size() - 1].second++;
        }
        else{
            rle.push_back(make_pair(A[i], 1));
        }
    }
    ll K = 0;
    rep(i, rle.size()){
        if (rle[i].first == 1) K++;
    }

    mint inv_2 = mint(1) / mint(2);
    vector<vector<mint>> dp(M + 1, vector<mint>((N + 1) / 2 + 1, 0));
    dp[0][K] = mint(1);
    for (ll i = 0; i < M; i++){
        for (ll j = 0; j <= (N + 1) / 2; j++){
            ll cnt1 = 2 * j;
            ll cnt2 = (N + 1) - cnt1;

            if (j > 0){
                dp[i + 1][j - 1] += dp[i][j] * mint(cnt1) * mint(cnt1 - 1) * inv_2;
            }
            dp[i + 1][j] += dp[i][j] * mint(cnt1) * mint(cnt2);
            if (j < (N + 1) / 2){
                dp[i + 1][j + 1] += dp[i][j] * mint(cnt2) * mint(cnt2 - 1) * inv_2;
            }
        }
    }
    cout << dp[M][0].val() << endl;
}