Submission #887064

#	Time	Username	Problem	Language	Result	Execution time	Memory
887064		dsyz	Global Warming (CEOI18_glo)	C++17	100 / 100	54 ms	8620 KiB

glo

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define MAXN (1000005)
int main() {
	ios_base::sync_with_stdio(false);cin.tie(0);
	ll N,X;
	cin>>N>>X;
	ll arr[N];
	for(ll i = 0;i < N;i++){
		cin>>arr[i];
	}
	//we can prove that it is always optimal to subtract x from prefix [0,i] because obviously we want the first few elements as small as possible, it will do no worse than subtracting x from [j,i]
	//since we are subtracting from the prefix, we should obviously subtract as much as possible which is x
	vector<ll> v(N,1e18);
	ll longestprefix[N];
	ll ans = 0;
	for(ll i = 0;i < N;i++){
		auto it = lower_bound(v.begin(),v.end(),arr[i]);
		v[it - v.begin()] = arr[i];
		longestprefix[i] = it - v.begin() + 1;
		ans = max(ans,longestprefix[i]);
	}
	v.clear();
	v = vector<ll>(N, 1e18);
	for(ll i = N - 1;i >= 0;i--){
		ll pos = lower_bound(v.begin(),v.end(),-arr[i] + X) - v.begin();
		ans = max(ans,longestprefix[i] + pos);
		ll insert_pos = lower_bound(v.begin(),v.end(),-arr[i]) - v.begin();
		v[insert_pos] = -arr[i];
	}
	cout<<ans<<'\n';
}

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 13 / 13
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 17 / 17
• Subtask 7: 25 / 25