Submission #1020180

#	Time	Username	Problem	Language	Result	Execution time	Memory
1020180		avighna	Strange Device (APIO19_strange_device)	C++17	100 / 100	634 ms	116020 KiB

strange_device

#include <bits/stdc++.h>

typedef long long ll;

int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);

  ll n, a, b;
  std::cin >> n >> a >> b;

  if (true) {
    // (2x % a, 0)
    // 2x % a == 0
    // if a is odd, then the cycle is of length a (the 2 will never
    // contribute)
    // if a is even, then the cycle of of length a/2
    ll cycle = a % 2 == 0 ? a / 2 : a;
    if (b != 0) {
      // w (B + 1) mod A = 0
      if (b / std::gcd(a, b + 1) >= (ll(1e18) + 1) / a) {
        cycle = ll(1e18) + 1;
      } else {
        cycle = a / std::gcd(a, b + 1) * b;
      }
    }
    std::vector<std::pair<ll, ll>> ranges;
    std::map<ll, ll> mp;
    while (n--) {
      ll l, r;
      std::cin >> l >> r;
      ll _l = l % cycle, _r = r % cycle;
      if (r - l + 1 >= cycle) {
        std::cout << cycle << "\n";
        return 0;
      }
      if (_l > _r) {
        ranges.push_back({_l, cycle - 1});
        ranges.push_back({0, _r});
      } else {
        ranges.push_back({_l, _r});
      }
    }
    for (auto &[l, r] : ranges) {
      mp[l] = std::max(mp[l], r);
    }
    ll right = 0;
    ll ans = 0;
    for (auto &i : mp) {
      if (i.second < right) {
        continue;
      }
      right = std::max(right, i.first);
      ans += i.second - right + 1;
      right = i.second + 1;
    }
    std::cout << ans << "\n";
    return 0;
  }

  std::set<std::pair<ll, ll>> st;
  while (n--) {
    ll l, r;
    std::cin >> l >> r;
    for (ll x = l; x <= r; ++x) {
      st.insert({(x + x / b) % a, x % b});
      //   std::cout << "(" << (x + x / b) % a << " " << x % b << "), ";
      //   std::cout << st.size() << "\n";
    }
  }
  std::cout << st.size() << "\n";
}

• Subtask 1: 10 / 10
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 5 / 5
• Subtask 5: 5 / 5
• Subtask 6: 20 / 20
• Subtask 7: 20 / 20
• Subtask 8: 30 / 30