Submission #1111608

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111608		justin271828	Trains (BOI24_trains)	C++14	37 / 100	2072 ms	3536 KiB

Main

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

int main() {
    long long N;
    cin >> N;
    if (N == 1) {
        cout << 1;
        return 0;
    }
    long long d[N];
    long long x[N];
    for (long long i = 0; i < N; i++) {
        cin >> d[i] >> x[i];
    }
    bool all = true;
    for (int i: d) if (i != 1) all = false;
    if (!all) {
        long long total[N];
        memset(total, 0, sizeof(total));
        total[0] = 1;
        for (long long i = 0; i < N; i++) {
            if (d[i] == 0) continue;
            for (long long j = 1; j <= x[i]; j++) {
                if (i+j*d[i] >= N) break;
                total[i+j*d[i]] += total[i];
                total[i+j*d[i]] %= 1000000007;
            }
        }
        long long ans = 0;
        for (long long i: total) ans += i;
        ans %= 1000000007;
        cout << ans;
        return 0;
    }
    long long diff[N];
    memset(diff, 0, sizeof(diff));
    diff[0] = 1;
    diff[1] = -1;
    long long dsum = 0;
    for (int i = 0; i < N-1; i++) {
        dsum += diff[i];
        if (dsum < 0) dsum += 1000000007;
        dsum %= 1000000007;
        diff[i+1] += dsum;
        if (diff[i+1] < 0) dsum += 1000000007;
        diff[i+1] %= 1000000007;
        if (i+1+x[i] < N) {
            diff[i+1+x[i]] -= dsum;
            if (diff[i+1+x[i]] < 0) dsum += 1000000007;
            diff[i+1+x[i]]%=1000000007;
        }
    }
    long long sum[N];
    sum[0] = 1;
    for (int i = 1; i < N; i++) {
        sum[i] = sum[i-1]+diff[i];
        if (sum[i] < 0) sum[i] += 1000000007;
        sum[i]%=1000000007;
    }
    long long ans = 0;
    for (long long i: sum) {
        ans += i;
        ans %= 1000000007;
    }
    cout << ans;
    return 0;
}

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