Submission #73960

#	Time	Username	Problem	Language	Result	Execution time	Memory
73960		zscoder	Homecoming (BOI18_homecoming)	C++17	100 / 100	412 ms	141676 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 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==0) return prefb[r];
	else return prefb[r]-prefb[l-1];
}
 
const ll INF=ll(1e18);
ll dp[4222222][2];
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];
		}
		dp[i][0]=dp[i][1]=-INF;
	}
	ans = max(0LL,prefa[n-1]-prefb[n-1]);
	for(int s=0;s<1;s++)
	{
		for(int i=s;i<n+s;i++)
		{
			for(int j=0;j<2;j++)
			{
				dp[i][j]=-INF;
			}
		}
		for(int i=s;i<n+s;i++)
		{
			if(i==s)
			{
				dp[i][0] = 0;
			}
			else
			{
				dp[i][0] = max(dp[i-1][0], dp[i-1][1]);
				dp[i][1] = max(dp[i-1][0] + a[i%n] - sumb(i%n, i%n+k-1), dp[i-1][1] + a[i%n] - b[(i+k-1)%n]);
			}
		}
		ans=max(ans,max(dp[n-1][0],dp[n-1][1]));
	}
	ll SS = sumb(0,k-1);
	for(int i=0;i<2*n;i++)
	{
		if(i%n<k) b[i%n]=0;
		prefa[i]=a[i%n]; prefb[i]=(i%n<k?0:b[i%n]);
		if(i>0) 
		{
			prefa[i]+=prefa[i-1]; prefb[i]+=prefb[i-1];
		}
		dp[i][0]=dp[i][1]=-INF;
	}
	for(int s=0;s<1;s++)
	{
		for(int i=s;i<n+s;i++)
		{
			for(int j=0;j<2;j++)
			{
				dp[i][j]=-INF;
			}
		}
		for(int i=s;i<n+s;i++)
		{
			if(i==s)
			{
				dp[i][1] = a[i%n] - SS;
			}
			else
			{
				dp[i][0] = max(dp[i-1][0], dp[i-1][1]);
				dp[i][1] = max(dp[i-1][0] + a[i%n] - sumb(i%n, i%n+k-1), dp[i-1][1] + a[i%n] - b[(i+k-1)%n]);
			}
		}
		ans=max(ans,max(dp[n-1][0],dp[n-1][1]));
	}
	return ans;
}
 

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