Submission #1243829

#	Time	Username	Problem	Language	Result	Execution time	Memory
1243829		lopkus	Trains (BOI24_trains)	C++20	8 / 100	701 ms	176012 KiB

Main

#include <bits/stdc++.h>

#define int long long

int mod = 1e9 + 7;

int add(int x, int y) {
  x += y;
  x %= mod;
  return x;
}

int S = 280;

const int N = 1e5 + 5;

struct fenwick {
  int t[2 * N];
  int query(int i) {
    int ans = 0;
    for(; i > 0; i -= i & - i) {
      ans = add(ans, t[i]);
    }
    return ans;
  }
  int query(int l, int r) {
    return query(r) - query(l - 1);
  }
  void update(int i, int v) {
    for(; i < N; i += i & - i) {
      t[i] = add(t[i], v);
    }
  }
  void update(int l, int r, int v) {
    update(l, v);
    update(r + 1, - v);
  }
}fenwick[281];

signed main() {
  int n;
  std::cin >> n;
  std::vector<int> d(n + 1), x(n + 1);
  for(int i = 1; i <= n; i++) {
    std::cin >> d[i] >> x[i];
  }
  std::vector<int> dp(n + 1, 0);
  dp[1] = 1;
  std::vector<std::vector<int>> pref(n + 1, std::vector<int>(S));
  for(int i = 1; i <= n; i++) {
    if(d[i] == 0) {
      continue;
    }
    int e = (n - i + 1) / d[i];
    for(int t = 1; t < S; t++) {
      if(i - t >= 0) {
        dp[i] = add(dp[i], fenwick[t].query(i));
      }
    }
    if(d[i] >= S) {
      for(int t = 1; t <= x[i] && i + t * d[i] <= n; t++) {
        dp[i + t * d[i]] = add(dp[i + t * d[i]], dp[i]);
      }
    }
    else {
      if(e <= S) {
        for(int t = 1; t <= x[i] && i + t * d[i] <= n; t++) {
          dp[i + t * d[i]] = add(dp[i + t * d[i]], dp[i]);
        }
      }
      else {
        int w = std::min(n, i + x[i] * d[i]);
        fenwick[d[i]].update(i, w, dp[i]);
      }
    }
  }
  int ans = 0;
  for(int i = 1; i <= n; i++) {
    ans = add(ans, dp[i]);
  }
  std::cout << ans;
}

• Subtask 1: 8 / 8
• Subtask 2: 0 / 13
• Subtask 3: 0 / 16
• Subtask 4: 0 / 34
• Subtask 5: 0 / 29