Submission #1124300

#	Time	Username	Problem	Language	Result	Execution time	Memory
1124300		votranngocvy	Trains (BOI24_trains)	C++20	100 / 100	282 ms	255072 KiB

Main

#include <bits/stdc++.h>
using namespace std;

#define int long long
const int N = 2e5 + 5;
const int block_size = 320;
const int mod = 1e9 + 7;
int a[N],b[N],dp[N],sum[325][N];
//sum[i][j]: so cach den dinh j voi buoc nhay co do dai i
signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i] >> b[i];
    for (int i = n; i > 0; i--) {
        dp[i] = 1;
        if (a[i] > block_size) {
            for (int j = 1; j <= b[i] && i + j * a[i] <= n; j++)
                dp[i] = (dp[i] + dp[i + j * a[i]]) % mod;
        }
        else if (a[i] > 0) {
            if (i + a[i] <= n) dp[i] = (dp[i] + sum[a[i]][i + a[i]]) % mod;
            if (i + (b[i] + 1) * a[i] <= n) dp[i] = (dp[i] - sum[a[i]][i + (b[i] + 1) * a[i]] + mod) % mod;
        }
        for (int j = 1; j <= block_size; j++) sum[j][i] = (sum[j][i + j] + dp[i]) % mod;
    }
    cout << dp[1] << "\n";
}

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