Submission #73912

#	Time	Username	Problem	Language	Result	Execution time	Memory
73912		zscoder	Homecoming (BOI18_homecoming)	C++17	62 / 100	1069 ms	149700 KiB

homecoming

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include "homecoming.h"

using namespace std;
using namespace __gnu_pbds;
 
#define fi first
#define se second
#define mp make_pair
#define pb push_back
 
typedef long long ll;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef long double ld; 
typedef tree<ii, null_type, less<ii>, rb_tree_tag, tree_order_statistics_node_update> pbds;

ll prefa[4222222];
ll prefb[4222222];
ll dp[2][2222222];
ll suma(int l, int r)
{
	if(l==0) return prefa[r];
	else return prefa[r]-prefa[l-1];
}

ll sumb(int l, int r)
{
	if(l>r) return 0;
	if(l==0) return prefb[r];
	else return prefb[r]-prefb[l-1];
}

const ll INF=ll(1e18);
ll solve(int n, int k, int *a, int *b)
{
	ll ans = 0;
	for(int i=0;i<2*n;i++)
	{
		prefa[i]=a[i%n]; prefb[i]=b[i%n];
		if(i>0) 
		{
			prefa[i]+=prefa[i-1]; prefb[i]+=prefb[i-1];
		}
	}
	ans = max(0LL,prefa[n-1]-prefb[n-1]);
	if(k==n) return ans;
	for(int s=0;s<k;s++)
	{
		//s must be a starting point
		for(int j=0;j<2;j++)
		{
			for(int z=0;z<n;z++)
			{
				dp[j][z]=-INF;
			}
		}
		dp[1][s] = a[s] - sumb(s,s+k-1);
		ans=max(ans,dp[1][s]);
		if(s==k-1)
		{
			dp[0][s]=0;
		}
		for(int i=s+1;i<n;i++)
		{
			dp[0][i] = max(dp[0][i-1], dp[1][i-1]);
			dp[1][i] = max(dp[0][i-1] + a[i] - sumb(i, min(n+s-1, i+k-1)), dp[1][i-1] + a[i] - (i+k-1>=n+s?0:b[(i+k-1)%n]));
			//cerr<<0<<' '<<s<<' '<<i<<' '<<dp[0][s][i]<<'\n';
			//cerr<<1<<' '<<s<<' '<<i<<' '<<dp[1][s][i]<<'\n';
			ans=max(ans,dp[0][i]);
			ans=max(ans,dp[1][i]);
		}
	}
	return ans;
}	

/*
int aaaa[2111111];
int bbbb[2111111];
int main()
{
	int n,k;
	cin>>n>>k;
	for(int i=0;i<n;i++)
	{
		cin>>aaaa[i];
	}
	for(int i=0;i<n;i++)
	{
		cin>>bbbb[i];
	}
	cout<<solve(n,k,aaaa,bbbb)<<'\n';
}
*/

• Subtask 1: 13 / 13
• Subtask 2: 18 / 18
• Subtask 3: 31 / 31
• Subtask 4: 0 / 38