Submission #815543

#	Time	Username	Problem	Language	Result	Execution time	Memory
815543		ZeroCool	Exam (eJOI20_exam)	C++14	100 / 100	331 ms	221908 KiB

exam

#include <bits/stdc++.h>  
#define INF 1e18
#define LL long long
#define int long long
using namespace std;
	
const int mod = 1e9 + 7;
const int inf = 1e18;
const int mxn = 1e5 +5;

struct FenwickTree{
	vector<int> bit;
	int n;
	FenwickTree(int _n){
		n = _n + 69;
		bit.resize(n,0);
	}
 
	void update(int pos,int val){
		for(pos++;pos<n;pos += pos & -pos)bit[pos] = max(bit[pos],val);
	}
 
	int query(int pos){
		int ans = 0;
		for(pos++;pos;pos -= pos & -pos)ans =  max(bit[pos],ans);
		return ans;
	}
};

int n;
	
int A[mxn];
int B[mxn];
int l[mxn];
int r[mxn];



void two_pointers(){
	int x = B[0];
	int res = 0;
	for(int i = 0;i<n;i++) {
		if(A[i] == x) {
			res++;
			int j = i - 1;
			while(j >= 0 && A[j] <= x) {
				j--;
				res++;
			}
			j = i + 1;
			while(j < n && A[j] <= x) {
				res++;
				j++;
			}
			i = j - 1;
		}
	}
	cout<<res<<endl;
	
}
	
int dp[5005][5005];
bool vis[5005][5005];
	
	
int f(int i,int j){
	if(i == -1 ||j == -1)return 0;
	if(vis[i][j])return dp[i][j];
	int ans = 0;
	if(A[i] == B[j] && l[i] < j && r[i] > j){
		ans = max(ans, f(i,j-1) + 1);
	}
	
	ans = max(ans , f(i-1,j));
	ans = max(ans, f(i,j-1));
	
	vis[i][j] = true;
	dp[i][j] = ans;
	return ans;
}
		
void solve(){
	cin>>n;
	
	set<int>s;
	int c[n+5];
	for(int i = 0;i<n;i++)cin>>A[i];
	for(int i = 0;i<n;i++){
		cin>>B[i];
		s.insert(B[i]);
	}
	
	for(int i = 0;i<n;i++)c[i+1] = A[i];
	
	c[0] = inf;
	c[n+1] = inf;
	stack<int> st;
	st.push(0);
	for(int i = 1;i<=n;i++){
		while(st.size() && (c[st.top()] <= c[i]))st.pop();
		l[i-1] = st.top() - 1;
		st.push(i);
	} 
	//st = stack<int>();
	while(st.size())st.pop();
	st.push(n+1);
	for(int i = n;i;i--){
		while(st.size() && (c[st.top()] <= c[i]))st.pop();
		//cout<<"tukaa"<<endl;
		r[i-1] = st.top() - 1;
		//if(r[i-1] >= n)r[i-1] = -1; 
		st.push(i);
	} 
	bool sub2 = true;
	for(int i = 1;i<n;i++){
		if(B[i] != B[0]){
			sub2 = false;
			break;
		}
	}
	
	if(sub2){
		two_pointers();
		return;
	}
	
	if(n <= 5000){
		cout<<f(n-1,n-1)<<endl;
		return;
	}

	map<int,int> mp;

	for(int i  = 0;i<n;i++){
		mp[A[i]] = i;
	}
	FenwickTree fwt(n);
	for(int i  = 0;i<n;i++){
		auto it = mp.find(B[i]);

		if(it != mp.end()){
			int idx = it->second;

			if(l[idx] < i and i < r[idx]) {
				int dp = fwt.query(idx);
				fwt.update(idx, dp + 1);
			}
		}
	}

	cout<<fwt.query(n-1)<<endl;
}
		
int32_t main() {  
	#ifdef ONLINE_JUDGE
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	#endif
	solve();
}   

• Subtask 1: 14 / 14
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 23 / 23
• Subtask 5: 16 / 16
• Subtask 6: 22 / 22