Submission #1097201

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097201		manhlinh1501	Trains (BOI24_trains)	C++17	100 / 100	315 ms	292760 KiB

Main

#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
const int MAXN = 1e5 + 5;
using pii = pair<int, int>;
const i64 MOD = 1e9 + 7;
const int BLOCK = 370;

int N;
pii a[MAXN];
i64 dp[MAXN];
i64 b[BLOCK][MAXN];

void add(i64 &a, i64 b) {
    a += b;
    if(a >= MOD) a -= MOD;
    if(a < 0) a += MOD;
}

signed main() {
#define TASK ""
    if(fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> N;

    for(int i = 1; i <= N; i++) cin >> a[i].first >> a[i].second;

    dp[1] = 1;

    for(int i = 1; i <= N; i++) {
        for(int j = 1; j < BLOCK; j++) {
            if(i >= j)
                add(b[j][i], b[j][i - j]);
        }

        for(int j = 1; j < BLOCK; j++)
            add(dp[i], b[j][i]);

        if(a[i].first == 0) continue;

        if(a[i].first >= BLOCK) {
            for(int j = 1; j <= a[i].second and i + j * a[i].first <= N; j++)
                add(dp[i + j * a[i].first], dp[i]);
        } else {
            if(i + a[i].first <= N)
                add(b[a[i].first][i + a[i].first], dp[i]);
            if(1LL * i + 1LL * a[i].first * a[i].second + a[i].first <= N)
                add(b[a[i].first][i + a[i].first * a[i].second + a[i].first], -dp[i]);
        }
    }

    i64 ans = 0;
    for(int i = 1; i <= N; i++) add(ans, dp[i]);

    cout << ans;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:23:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:24:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   24 |         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