제출 #1118572

#제출 시각아이디문제언어결과실행 시간메모리
1118572dynam1cTrains (BOI24_trains)C++17
16 / 100
52 ms4920 KiB
#include <bits/stdc++.h>
using namespace std;
int mod = 1e9+7;
int main() {
  int n;
  cin >> n;
  vector<vector<int>> ends(n+1);
  vector<int> ans(n);
  ans[0] = 1;

  for (int i = 0; i < n; i++) {
    int d, x;
    cin >> d >> x;
    int r = min(x+i, n);
    ends[r].push_back(i);
  }

  int cur = 0;
  for (int i = 0; i < n; i++) {
    if (i > 0)
      ans[i] = cur;

    cur = (cur + ans[i]) % mod;
    for (auto j : ends[i])
      cur = (cur - ans[j] + mod) % mod;
  }

  cout << accumulate(ans.begin(), ans.end(), 0LL) % mod << endl;
}
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