提出 #69710421

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ソースコード 拡げる

#include <bits/stdc++.h>
using namespace std;
// #define int long long
#define rep(i, j, k) for(int i = (j); i <= (k); i++)
#define per(i, j, k) for(int i = (j); i >= (k); i--)
#define pb emplace_back
#define fi first
#define se second
using vi = vector<int>;
using pi = pair<int, int>;

template<typename T0, typename T1> bool chmin(T0 &x, const T1 &y){
	if(y < x){x = y; return true;} return false;
}
template<typename T0, typename T1> bool chmax(T0 &x, const T1 &y){
	if(x < y){x = y; return true;} return false;
}

template<typename T> void debug(char *s, T x){
	cerr << s <<" = "<< x <<endl;
}
template<typename T, typename ...Ar> void debug(char *s, T x, Ar... y){
	int dep = 0;
	while(!(*s == ',' && dep == 0)){
		if(*s == '(') dep++;
		if(*s == ')') dep--;
		cerr << *s++;
	}
	cerr <<" = "<< x <<",";
	debug(s + 1, y...);
}
#define gdb(...) debug((char*)#__VA_ARGS__, __VA_ARGS__)


using u32 = uint32_t;
using u64 = uint64_t;
constexpr int mod = 998244353;
struct mint{
	u32 x;
	
	mint(): x(0){}
	mint(int _x){
		_x %= mod;
		if(_x < 0) _x += mod;
		x = _x;
	}

	u32 val()const {
		return x;
	}
	mint qpow(int y = mod - 2)const {
		assert(y >= 0);
		mint t = *this, res = 1;
		while(y){
			if(y % 2) res *= t;
			t *= t;
			y /= 2;
		}
		return res;
	}

	mint& operator += (const mint &B){
		if((x += B.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator -= (const mint &B){
		if((x -= B.x) >= mod) x += mod;
		return *this;
	}
	mint& operator *= (const mint &B){
		x = (u64)x * B.x % mod;
		return *this;
	}
	mint& operator /= (const mint &B){
		return *this *= B.qpow();
	}
	friend mint operator + (const mint &A, const mint &B){
		return mint(A) += B;
	}
	friend mint operator - (const mint &A, const mint &B){
		return mint(A) -= B;
	}
	friend mint operator * (const mint &A, const mint &B){
		return mint(A) *= B;
	}
	friend mint operator / (const mint &A, const mint &B){
		return mint(A) /= B;
	}
	mint operator - ()const {
		return mint() - *this;
	}
};

const int N = 1e6 + 5;
mint fac[N], ifac[N];
void init(){
	fac[0] = ifac[0] = 1;
	rep(i, 1, N - 1){
		fac[i] = fac[i - 1] * i;
		ifac[i] = 1 / fac[i];
	}
}
mint C(int m, int n){
	return fac[m] * ifac[n] * ifac[m - n];
}

signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	init();
	int l, k, n;
	cin >> l >> k >> n;
	vi a(n);
	for(auto &x:a){
		cin >> x;
	}
	mint ans = 0;
	rep(i, 0, n - 1){
		int c0 = 0, c1 = 0;
		rep(j, 0, i - 1){
			c0 += (a[j] + k > a[i]);
			c1 += (a[i] + k - l > a[j]);
		}
		mint t = c0 + c1 + 2;
		if(c0 == 0){
			t += 1;
		}
		if(c1 == 0){
			t += 1;
		}
		ans += t;
	}
	ans *= mint(2).qpow(n - 3 + (mod - 1));

	cout << ans.val() <<'\n'; 
}

提出情報

ジャッジ結果