Submission #1051352

#	Time	Username	Problem	Language	Result	Execution time	Memory
1051352		Whisper	Trains (BOI24_trains)	C++17	100 / 100	206 ms	269288 KiB

Main

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)


constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

/*
    Phu Trong from Nguyen Tat Thanh High School for gifted student
*/

template <class X, class Y>
    bool minimize(X &x, const Y &y){
        X eps = 1e-9;
        if (x > y + eps) {x = y; return 1;}
        return 0;
    }

template <class X, class Y>
    bool maximize(X &x, const Y &y){
        X eps = 1e-9;
        if (x + eps < y) {x = y; return 1;}
        return 0;
    }
#define MAX                 100005
#define BLOCK_SIZE          333
int numTrain;


pair<int, int> A[MAX]; //(time between each stop point, num stop point)

int dp[MAX];
void add(int &x, int y){
    x += y;
    if (x >= Mod) x %= Mod;
    while(x < 0) x += Mod;
}

int pref[MAX][BLOCK_SIZE + 5];

void process(void){
    cin >> numTrain;
    for (int i = 1; i <= numTrain; ++i) cin >> A[i].first >> A[i].second;
    dp[1] = 1;

    int ans = 0;
    for (int i = 1; i <= numTrain; ++i){
        for (int v = 1; v <= BLOCK_SIZE; ++v){
            if(i >= v) add(pref[i][v], pref[i - v][v]);
            add(dp[i], pref[i][v]);
        }
        if (A[i].first >= BLOCK_SIZE){
            int x = A[i].second;
            for (int v = i + A[i].first; v <= numTrain && x > 0; v += A[i].first, x--){
                add(dp[v], dp[i]);
            }
        }
        else{
            add(pref[i][A[i].first], dp[i]);
            int fin = min(numTrain + 1, i + (A[i].first * (A[i].second + 1)));
            add(pref[fin][A[i].first], -dp[i]);
        }
        add(ans, dp[i]);
    }
    cout << ans;
}
signed main(){
    #define name "Whisper"
    cin.tie(nullptr) -> sync_with_stdio(false);
    //freopen(name".inp", "r", stdin);
    //freopen(name".out", "w", stdout);
    process();
    return (0 ^ 0);
}

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