Submission #1084748

#TimeUsernameProblemLanguageResultExecution timeMemory
1084748zxciganTrains (BOI24_trains)C++17
21 / 100
2066 ms1976 KiB
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define int long long
const int N = 2e5;
const int mod = 1e9 + 7;
int dp[N];
int32_t main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif // LOCAL
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    dp[1] = 1;
    int s = 0;
    for (int i = 1; i <= n; ++i) {
        int x, d;
        cin >> d >> x;
        if (x && d) {
            for (int j = 1; j <= x; ++j) {
                if (i + d * j > n) break;
                (dp[i + d * j] += dp[i]) %= mod;
            }
        }
        (s += dp[i]) %= mod;
    }
    cout << s << '\n';
}
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