Submission #1111466

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111466		gelastropod	Trains (BOI24_trains)	C++14	37 / 100	2070 ms	6492 KiB

Main

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

vector<int> tree;

void upd(int n, int x)
{
    while (n < tree.size())
    {
        tree[n] += x;
        tree[n] %= 1000000007;
        n += n & (-n);
    }
}

int qry(int a)
{
    if (a == 0)
        return 0;
    if (a >= tree.size())
        return qry(tree.size() - 1);
    int ans = 0;
    while (a > 0)
    {
        ans += tree[a];
        ans %= 1000000007;
        a -= a & (-a);
    }
    return ans;
}

vector<pair<int, int>> vals;
vector<int> dp;

int ways(int n)
{
    if (dp[n] != -1) return dp[n];
    if (vals[n].first == 0 || n + vals[n].first >= (int)dp.size()) return dp[n] = 1;
    int ans = 1;
    for (int i = n + vals[n].first, t = 0; i < (int)dp.size() && t < vals[n].second; i += vals[n].first, t++)
    {
        ans += ways(i);
        ans %= 1000000007;
    }
    return dp[n] = ans;
}

signed main()
{
    int N, a, b;
    cin >> N;
    tree = vector<int>(N + 1, 0);
    dp = vector<int>(N, -1);
    bool huh = false;
    for (int i = 0; i < N; i++)
    {
        cin >> a >> b;
        vals.push_back({a, b});
        if (a != 1)
            huh = true;
    }
    if (huh)
    {
        cout << ways(0) << '\n';
    }
    else
    {
        for (int i = N - 1; i >= 0; i--)
        {
            if (i + 1 >= N)
                upd(i + 1, 1);
            else
                upd(i + 1, (1 + qry(i + 1 + vals[i].second) - qry(i)) % 1000000007);
        }
        cout << qry(1) << '\n';
    }
}

Compilation message (stderr)

Main.cpp: In function 'void upd(long long int, long long int)':
Main.cpp:9:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    9 |     while (n < tree.size())
      |            ~~^~~~~~~~~~~~~
Main.cpp: In function 'long long int qry(long long int)':
Main.cpp:21:11: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 |     if (a >= tree.size())
      |         ~~^~~~~~~~~~~~~~

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