Submission #1097186

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097186		manhlinh1501	Trains (BOI24_trains)	C++17	100 / 100	343 ms	233884 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 = 400;
 
int N;
pii a[MAXN];
i64 dp[MAXN];
i64 b[BLOCK][MAXN];
i64 c[BLOCK][BLOCK];
 
void add(i64 &a, i64 b) {
    a += b;
    if(a >= MOD) a -= MOD;
    if(a < 0) a += MOD;
}

void update(i64 p, int x, i64 res) {
    if(p > N) return;
 
    add(b[x][p], res);
}
 
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++) {
            add(c[j][i % j], b[j][i]);
            add(dp[i], c[j][i % j]);
        }
        if(a[i].first == 0) continue;
 
        if(a[i].first < BLOCK) {
            update(1LL * i + a[i].first, a[i].first, dp[i]);
            update(1LL * i + 1LL * a[i].first * a[i].second + a[i].first, a[i].first, -dp[i]);
        } else {
            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]);
        }
    }
 
    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:30:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:31:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |         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