Submission #974428

#	Time	Username	Problem	Language	Result	Execution time	Memory
974428		rolandpetrean	Remittance (JOI19_remittance)	C++17	55 / 100	186 ms	64040 KiB

remittance

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define int ll

#define endl '\n'
#define pb push_back
using pi = array<int, 2>;

const int N = 1e6 + 5, MOD = 1e9 + 7;

int p2[N];
void prec() {
  p2[0] = 1;
  for (int i = 1; i < N; ++i) p2[i] = p2[i - 1] * 2 % MOD;
}
int binpow(int a, int b) {
  int res = 1;
  while (b) {
    if (b & 1) res = res * a % MOD;
    a = a * a % MOD;
    b >>= 1;
  }
  return res;
}
int modinv(int n) {
  return binpow(n, MOD - 2);
}

int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  
  prec();
  
  int n;
  cin >> n;
  
  vector<int> a(n), b(n), c(n);
  for (int i = 0; i < n; ++i) {
    cin >> a[i] >> b[i];
    c[i] = b[i] - a[i];
  }
  
  assert(n <= 20);
  
  vector<int> in(n);
  for (int i = 0; i < n; ++i) {
    in[0] = (in[0] - p2[i] * c[i] % MOD + MOD) % MOD;
  }
  in[0] = (in[0] * modinv(p2[n] - 1) % MOD + MOD) % MOD;
  
  for (int i = 1; i < n; ++i) {
    int x = in[i - 1] - c[i - 1];
    if (x % 2 != 0) {
      cout << "No";
      return 0;
    }
    in[i] = x / 2;
  }
  
  for (int i = 0; i < n; ++i) {
    if (in[i] < 0) {
      cout << "No";
      return 0;
    }
  }
  
  bool pushed = true;
  while (pushed) {
    pushed = false;
    for (int i = 0; i < n; ++i) {
      int j = (i + 1) % n;
      
      int push = min(in[j], a[i] / 2);
      a[i] -= 2 * push;
      in[j] -= push;
      a[j] += push;

      if (push != 0) pushed = true;
    }
  }
  
  for (int i = 0; i < n; ++i) {
    if (in[i] != 0) {
      cout << "No";
      return 0;
    }
  }
  
  cout << "Yes";
}

• Subtask 1: 15 / 15
• Subtask 2: 40 / 40
• Subtask 3: 0 / 45