Submission #1033930

#	Time	Username	Problem	Language	Result	Execution time	Memory
1033930		_shr104	Trains (BOI24_trains)	C++14	100 / 100	207 ms	258752 KiB

Main

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double ld;
#define pb push_back
#define pf push_front
#define fi first
#define se second
const ll mod = 1e9+7, mxn = 1e5+7, block = 320;
ll d[mxn], x[mxn], pfs[mxn][block+7], dp[mxn];
signed main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    // freopen("test.inp","r",stdin); freopen("test.out","w",stdout); freopen("test.err","w",stderr);
    ll n, ans = 0; cin >> n; dp[1] = 1;
    for (ll i = 1; i <= n; i++)
    {
        for (ll j = 1; j <= block; j++)
        {
            if (i >= j) 
            {
                pfs[i][j] += pfs[i-j][j];
                if (pfs[i][j] >= mod) pfs[i][j] -= mod;
            }
            dp[i] += pfs[i][j];
            if (dp[i] >= mod) dp[i] -= mod;
        }
        cin >> d[i] >> x[i];
        if (!d[i]) continue;
        if (d[i] > block)
        {
            for (ll j = i+d[i]; j <= min(n, i+x[i]*d[i]); j += d[i])
            {
                dp[j] += dp[i];
                if (dp[j] >= mod) dp[j] -= mod;
            } 
        }
        else
        {
            if (i+d[i] > n) continue;
            pfs[i+d[i]][d[i]] += dp[i];
            if (pfs[i+d[i]][d[i]] >= mod) pfs[i+d[i]][d[i]] -= mod;
            if (i+(x[i]+1)*d[i] <= n) 
            {
                pfs[i+(x[i]+1)*d[i]][d[i]] -= dp[i];
                if (pfs[i+(x[i]+1)*d[i]][d[i]] < 0) pfs[i+(x[i]+1)*d[i]][d[i]] += mod;
            }
        }
    }
    for (ll i = 1; i <= n; i++)
    {
        ans += dp[i];
        if (ans >= mod) ans -= mod;
    }
    cout << ans << '\n';
}

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