Submission #1243835

#	Time	Username	Problem	Language	Result	Execution time	Memory
1243835		lopkus	Trains (BOI24_trains)	C++20	58 / 100	192 ms	225828 KiB

Main

#include <bits/stdc++.h>

#define int long long

int mod = 1e9 + 7;

int add(int x, int y) {
  x += y;
  if(x < 0) {
    x += mod;
  }
  if(x >= mod) {
    x %= mod;
  }
  return x;
}

int S = 280;

const int N = 1e5 + 5;

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 + 2, 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) {
        pref[i][t] = add(pref[i][t], pref[i - t][t]);
        dp[i] = add(dp[i], pref[i][t]);
      }
    }
    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]);
        pref[i][d[i]] = add(pref[i][d[i]], dp[i]);
        if(w + d[i] <= n) {
          pref[w + d[i]][d[i]] = add(pref[w + d[i]][d[i]], - 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: 16 / 16
• Subtask 4: 34 / 34
• Subtask 5: 0 / 29