Submission #1303474

#	Time	Username	Problem	Language	Result	Execution time	Memory
1303474		red_souls	Trains (BOI24_trains)	C++20	100 / 100	81 ms	7456 KiB

Main

#include <bits/stdc++.h>
#define ll long long
#define task "TRAINS"
using namespace std;

const int N = 1e5 + 16;
const ll mod = 1e9 + 7;
int n;
ll d[N], x[N];

ll add(ll a, ll b) {
    a += b;
    if (a >= mod) {
        a -= mod;
    }
    return a;
}

ll sub(ll a, ll b) {
    a -= b;
    if (a < 0) {
        a += mod;
    }
    return a;
}

namespace sub5 {

    ll result, dp[N], s[320][320];
    vector <int> events[N];
    int BLOCKSIZE;

    void solve() {
        BLOCKSIZE = sqrt(n);
        dp[1] = 1;
        for (int i = 1; i <= n; i++) {
            for (auto x : events[i]) {
                s[d[x]][x % d[x]] = sub(s[d[x]][x % d[x]], dp[x]);
            }
            for (int j = 1; j < BLOCKSIZE; j++) {
                dp[i] = add(dp[i], s[j][i % j]);
            }
            if (d[i] == 0) {
                continue;
            }
            if (d[i] >= BLOCKSIZE) {
                for (int j = 1; j <= x[i] && i + j * d[i] <= n; j++) {
                    dp[i + j * d[i]] = add(dp[i + j * d[i]], dp[i]);
                }
            }
            else {
                s[d[i]][i % d[i]] = add(s[d[i]][i % d[i]], dp[i]);
                events[min(1LL * n, d[i] * x[i] + i) + 1].push_back(i);
            }
        }
        for (int i = 1; i <= n; i++) {
            result = add(result, dp[i]);
        }
        cout << result;
    }
}

int main() {
    ios_base :: sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }

    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> d[i] >> x[i];
    }
    sub5 :: solve();

    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:69:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:70:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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