Submission #1267607

#	Time	Username	Problem	Language	Result	Execution time	Memory
1267607		pandaa73	Trains (BOI24_trains)	C++20	71 / 100	2089 ms	367816 KiB

Main

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

#define lf "\n"
#define ff endl
#define _ << ' ' <<
#define all(x) begin(x),end(x)
#define rall(x) rbegin(x),rend(x)

#define infos(str) do { fprintf(stderr, str"\n"); } while(0)
#define infor(str, ...) do { fprintf(stderr, str, __VA_ARGS__); } while(0)
#define infof(str, ...) do { fprintf(stderr, str"\n", __VA_ARGS__); } while(0)

#ifndef DEBUG

#undef infos
#undef infor
#undef infof

#define infos(str)
#define infor(str, ...)
#define infof(str, ...)

#endif

using ll = long long;

constexpr int LOG = 20;
constexpr int MOD = 1e9+7;
constexpr int MAXN = 1e5+7;

int main(void) {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int N; cin >> N;

    vector<ll> V(N), K(N);
    for(int i = 0; i < N; ++i)
        cin >> V[i] >> K[i];

    vector<ll> dp(N);
    vector<unordered_map<int, ll>> pfx(N);

    auto calc = [&](ll i, ll k, auto &&calc) -> ll {
        if(i >= N) return 0;

        if(pfx[i].find(k) != pfx[i].end())
            return pfx[i][k];

        infof("calc: %d [%d]", i, k);

        return pfx[i][k] = (dp[i] + calc(i + k, k, calc)) % MOD;
    };

    auto sum = [&](ll i, ll v, ll k) {
        ll mx_idx = (i + V[i] * ((N - 1 - i) / V[i]));

        ll l = min(mx_idx, i) + v, r = min(mx_idx, i + v * k) + v;

        ll pfx_l;
        if(l >= N)
            pfx_l = 0;
        else pfx_l = pfx[l][v];

        ll pfx_r;
        if(r >= N)
            pfx_r = 0;
        else pfx_r = pfx[r][v];

        infof("sum: i = %lld | v = %lld | k = %lld", i, v, k);
        infof("... -> (l, r) = [%lld, %lld): [%lld, %lld)", l, r, pfx_l, pfx_r);

        return (pfx_l - pfx_r + MOD) % MOD;
    };

    for(int i = N - 1; i >= 0; i--) {
        dp[i] = 1;

        if(V[i] == 0 || i + V[i] >= N) continue;

        calc(i + V[i], V[i], calc);

        dp[i] += sum(i, V[i], K[i]);
    }

    for(int i = 0; i < N; ++i) {
        infos("-------");
        infof("%d: %lld", i, dp[i]);
        for(auto [k, v]: pfx[i])
            infof("... -> %d: %lld", k, v);
        infos("");
    }

    cout << dp[0] << lf;
}

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