Submission #5198838


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#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
//#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
template<int MOD> struct ModInt {
    static const int Mod = MOD; unsigned x; ModInt() : x(0) { }
    ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    int get() const { return (int)x; }
    ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
    ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
    ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
    ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
    ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
    ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
    ModInt inverse() const { long long a = x, b = MOD, u = 1, v = 0;
        while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); }
        return ModInt(u); }
    bool operator==(ModInt that) const { return x == that.x; }
    bool operator!=(ModInt that) const { return x != that.x; }
    ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; }
};
template<int MOD> ostream& operator<<(ostream& st, const ModInt<MOD> a) { st << a.get(); return st; };
template<int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
    ModInt<MOD> r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r; }
template<typename T, int FAC_MAX> struct Comb { vector<T> fac, ifac;
    Comb(){fac.resize(FAC_MAX,1);ifac.resize(FAC_MAX,1);rep(i,1,FAC_MAX)fac[i]=fac[i-1]*i;
        ifac[FAC_MAX-1]=T(1)/fac[FAC_MAX-1];rrep(i,FAC_MAX-2,1)ifac[i]=ifac[i+1]*T(i+1);}
    T aPb(int a, int b) { if (b < 0 || a < b) return T(0); return fac[a] * ifac[a - b]; }
    T aCb(int a, int b) { if (b < 0 || a < b) return T(0); return fac[a] * ifac[a - b] * ifac[b]; }
    T nHk(int n, int k) { if (n == 0 && k == 0) return T(1); if (n <= 0 || k < 0) return 0;
        return aCb(n + k - 1, k); } // nHk = (n+k-1)Ck : n is separator
    T pairCombination(int n) {if(n%2==1)return T(0);return fac[n]*ifac[n/2]/(T(2)^(n/2));}
    // combination of paris for n
}; 
typedef ModInt<1000000007> mint;
/*---------------------------------------------------------------------------------------------------
            ∧_∧
      ∧_∧  (´<_` )  Welcome to My Coding Space!
     ( ´_ゝ`) /  ⌒i
    /   \     | |
    /   / ̄ ̄ ̄ ̄/  |
  __(__ニつ/     _/ .| .|____
     \/____/ (u ⊃
---------------------------------------------------------------------------------------------------*/






Comb<mint, 202020> com;
//---------------------------------------------------------------------------------------------------
void _main() {
	int Q; cin >> Q;
	rep(q, 0, Q) {
		ll N, K;
		cin >> N >> K;

		if (N % 2 == 0) {
			N /= 2;

			ll zero1 = (N * 2 + sqrt(N * 2 * N * 2 - 4LL * 2 * K) + 0.1) / 4LL;
			ll zero2 = (N * 2 - sqrt(N * 2 * N * 2 - 4LL * 2 * K) + 0.1) / 4LL;

			if (2LL * (N - zero1) * zero1 != K) {
				printf("0\n");
				continue;
			}

			if (2LL * (N - zero2) * zero2 != K) {
				printf("0\n");
				continue;
			}

			mint ans = 0;

			if (zero1 == zero2) ans = com.aCb(N, zero1);
			else ans = com.aCb(N, zero1) + com.aCb(N, zero2);

			printf("%d\n", ans.get());
		}
		else {
			N /= 2;

			mint ans = 0;

			// xxxx1xxxx
			while (1) {
				ll zero1 = (N * 2 + 1 + (int)(sqrt((N * 2 + 1) * (N * 2 + 1) - 4LL * 2 * K) + 0.1)) / 4LL;
				ll zero2 = (N * 2 + 1 - (int)(sqrt((N * 2 + 1) * (N * 2 + 1) - 4LL * 2 * K) + 0.1)) / 4LL;

				if (2LL * (N - zero1) * zero1 + zero1 == K) {
					ans += com.aCb(N, zero1);
				}
				if (2LL * (N - zero2) * zero2 + zero2 == K and zero1 != zero2) {
					ans += com.aCb(N, zero2);
				}
				break;
			}

			// xxxx0xxxx
			while (1) {
				ll zero1 = (N * 2 - 1 + sqrt((N * 2 - 1) * (N * 2 - 1) - 4LL * 2 * (K-N)) + 0.1) / 4LL;
				ll zero2 = (N * 2 - 1 - sqrt((N * 2 - 1) * (N * 2 - 1) - 4LL * 2 * (K-N)) + 0.1) / 4LL;

				if (2LL * (N - zero1) * zero1 + N - zero1 == K) {
					ans += com.aCb(N, zero1);
				}
				if (2LL * (N - zero2) * zero2 + N - zero2 == K and zero1 != zero2) {
					ans += com.aCb(N, zero2);
				}
				break;
			}

			printf("%d\n", ans.get());
		}
	}
}

Submission Info

Submission Time
Task J - ヌクレオチド
User hamayanhamayan
Language C++14 (GCC 5.4.1)
Score 500
Code Size 5357 Byte
Status AC
Exec Time 33 ms
Memory 2432 KB

Judge Result

Set Name Sample Subtask1
Score / Max Score 0 / 0 500 / 500
Status
AC × 2
AC × 11
Set Name Test Cases
Sample sample_01.txt, sample_02.txt
Subtask1 sample_01.txt, sample_02.txt, sub1_01.txt, sub1_02.txt, sub1_03.txt, sub1_04.txt, sub1_05.txt, sub1_06.txt, sub1_07.txt, sub1_08.txt, sub1_09.txt
Case Name Status Exec Time Memory
sample_01.txt AC 4 ms 1792 KB
sample_02.txt AC 4 ms 1792 KB
sub1_01.txt AC 33 ms 2432 KB
sub1_02.txt AC 33 ms 2432 KB
sub1_03.txt AC 33 ms 2432 KB
sub1_04.txt AC 33 ms 2432 KB
sub1_05.txt AC 33 ms 2432 KB
sub1_06.txt AC 4 ms 1792 KB
sub1_07.txt AC 4 ms 1792 KB
sub1_08.txt AC 4 ms 1792 KB
sub1_09.txt AC 4 ms 1792 KB