#326353 (C++14) No.802 だいたい等差数列

• 問題: No.802 だいたい等差数列
• ユーザー: fumiphys
• 提出日時: 2019-03-19 23:13:43
• 言語: C++14 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 35 ms / 2,000 ms
• コード長: 2,285 bytes
• コンパイル時間: 1,117 ms
• コンパイル使用メモリ: 111,284 KB
• 実行使用メモリ: 34,736 KB
• 最終ジャッジ日時: 2024-09-14 13:13:26
• 合計ジャッジ時間: 3,333 ms
• ジャッジサーバーID （参考情報）: judge5 / judge4

ファイルパターン	結果
sample	AC * 4
other	AC * 30

ソースコード

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// includes
#include <cstdio>
#include <cstdint>
#include <iostream>
#include <iomanip>
#include <string>
#include <queue>
#include <stack>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <utility>
#include <functional>
#include <cmath>
#include <climits>
#include <bitset>
#include <list>
#include <random>
// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
using namespace std;
//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;
// solve
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(a > b){a = b; return 1;} return 0;}
ll fac[2000001], inv[2000001];
template <typename T>
T power(T a, T n, T mod) {
  T res = 1;
  T tmp = n;
  T curr = a;
  while(tmp){
    if(tmp % 2 == 1){
      res = (T)((ll)res * curr % mod);
    }
    curr = (T)((ll)curr * curr % mod);
    tmp >>= 1;
  }
  return res;
}
ll comb(ll n, ll k){
  ll res = 1;
  res = res * fac[n] % mod;
  res = res * inv[k] % mod;
  res = res * inv[n-k] % mod;
  return res;
}
ll h(ll n, ll k){
  return comb(n + k - 1, n);
}
int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  ll n, m, d1, d2;
  cin >> n >> m >> d1 >> d2;
  fac[0] = 1;
  for(int i = 1; i < 2000001; i++)fac[i] = i * fac[i-1] % mod;
  inv[2000000] = power<ll>(fac[2000000], mod - 2, mod);
  for(int i = 1999999; i >= 0; i--)inv[i] = (i + 1) * inv[i+1] % mod;
  ll res = 0;
  for(int p = 0; p < n; p++){
    ll M = m - (n - 1) * d1 - 1 - p * (d2 - d1 + 1);
    if(M < 0)continue;
    ll tmp = comb(n - 1, p) * h(M, n + 1);
    if(p % 2 == 0)res = (res + tmp) % mod;
    else res = (res - tmp) % mod;
    if(res < 0)res += mod;
  }
  cout << res << endl;
    return 0;
}
 
 
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