Submission #1026271

#	Time	Username	Problem	Language	Result	Execution time	Memory
1026271		mareksb	Trains (BOI24_trains)	C++17	100 / 100	192 ms	259068 KiB

Main

#include <bits/stdc++.h>

using namespace std;
constexpr int64_t N = 1e5+5;
constexpr int64_t mod = 1e9+7;
int64_t dp[N+5]{};//number of paths starting from i
constexpr int64_t d=320;
int64_t c[N+5][d+5]{};//sum dp given (start pos, step size)
int main() {
    int64_t n;
    cin>>n;
    int64_t a[n+1],b[n+1];
    for(int64_t i=1;i<=n;i++){
        cin>>a[i]>>b[i];
    }
    for(int64_t i=n;i>0;i--){
        dp[i]=1;
        if(a[i]){
            if(a[i]>=d){
                for(int64_t j=1;j<=b[i];j++){
                        int64_t pos=i+j*a[i];
                        if(pos>n)break;
                        dp[i]=(dp[i]+dp[pos])%mod;
                }
            }
            else{
                int64_t fin = min(i+a[i]*b[i],n);
                dp[i]=(dp[i]+c[i][a[i]]-c[fin][a[i]]+mod)%mod;
            }
        }
        //update c state
        for(int64_t j=1;j<d;j++){
            if(i-j<1)break;
            c[i-j][j]=(c[i][j]+dp[i])%mod;
        }
    }
    cout<<dp[1]%mod<<' ';

}

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