Submission #1150927

#	Time	Username	Problem	Language	Result	Execution time	Memory
1150927		SmuggingSpun	Exam (eJOI20_exam)	C++20	100 / 100	81 ms	4612 KiB

exam

#include<bits/stdc++.h>
#define taskname "C"
using namespace std;
template<class T>void maximize(T& a, T b){
	if(a < b){
		a = b;
	}
}
const int lim = 1e5 + 5;
int n, N, a[lim], b[lim];
vector<int>compress;
namespace sub2{
	void solve(){
		int ans = 0;
		for(int i = 1; i <= n; i++){
			if(a[i] > b[1]){
				continue;
			}
			if(a[i] == b[1]){
				int l = i;
				ans++;
				while(--l > 0 && a[l] <= b[1]){
					ans++;
				}
				while(++i <= n && a[i] <= b[1]){
					ans++;
				}
			}
		}
		cout << ans;
	}
}
namespace sub3{
	const int lim = 5e3 + 5;
	int dp[2][lim << 1];
	bitset<lim << 1>app;
	void solve(){
		app.reset();
		for(int i = 1; i <= n; i++){
			app.set(a[i]);
		}
		memset(dp, 0, sizeof(dp));
		bool cur = true, pre = false;
		for(int i = 1; i <= n; i++){
			swap(cur, pre);
			fill(dp[cur], dp[cur] + a[i], 0);
			for(int j = a[i]; j <= N; j++){
				dp[cur][j] = max(dp[cur][j - 1], (app.test(j) ? dp[pre][j] + int(j == b[i]) : 0));
			}
		}
		cout << dp[cur][N];
	}
}
namespace sub4{
	int p[lim << 1], bit[lim << 1], left[lim], right[lim];
	void update(int p, int x){
		for(; p <= N; p += p & -p){
			maximize(bit[p], x);
		}
	}
	int get(int p){
		int ans = 0;
		for(; p > 0; p -= p & -p){
			maximize(ans, bit[p]);
		}
		return ans;
	}
	void solve(){
		memset(p, -1, sizeof(p));
		stack<int>st;
		for(int i = 1; i <= n; st.push(i++)){
			p[a[i]] = i;
			while(!st.empty() && a[i] > a[st.top()]){
				st.pop();
			}
			left[i] = (st.empty() ? 1 : st.top() + 1);
		}
		while(!st.empty()){
			st.pop();
		}
		for(int i = n; i > 0; st.push(i--)){
			while(!st.empty() && a[i] > a[st.top()]){
				st.pop();
			}
			right[i] = (st.empty() ? n : st.top() - 1);
		}
		memset(bit, 0, sizeof(bit));
		for(int i = 1; i <= n; i++){
			if(p[b[i]] != -1 && left[p[b[i]]] <= i && right[p[b[i]]] >= i){
				update(p[b[i]], get(p[b[i]]) + 1);
			}
		}
		cout << get(N);
	}
}
namespace sub156{
	const int lim = 5e3 + 5;
	int dp[lim], left[lim], right[lim];
	void solve(){
		stack<int>st;
		for(int i = 1; i <= n; st.push(i++)){
			while(!st.empty() && a[i] > a[st.top()]){
				st.pop();
			}
			left[i] = (st.empty() ? 1 : st.top() + 1);
		}
		while(!st.empty()){
			st.pop();
		}
		for(int i = n; i > 0; st.push(i--)){
			while(!st.empty() && a[i] > a[st.top()]){
				st.pop();
			}
			right[i] = (st.empty() ? n : st.top() - 1);
		}
		memset(dp, 0, sizeof(dp));
		for(int i = 1; i <= n; i++){
			for(int j = 1; j <= n; j++){
				maximize(dp[j], dp[j - 1] + int(a[i] == b[j] && left[i] <= j && right[i] >= j));
			}
		}
		cout << dp[n];
	}
}
int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	if(fopen(taskname".inp", "r")){
		freopen(taskname".inp", "r", stdin);
	}
	cin >> n;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
		compress.emplace_back(a[i]);
	}
	for(int i = 1; i <= n; i++){
		cin >> b[i];
		compress.emplace_back(b[i]);
	}
	sort(compress.begin(), compress.end());
	compress.resize(unique(compress.begin(), compress.end()) - compress.begin());
	for(int i = 1; i <= n; i++){
		a[i] = lower_bound(compress.begin(), compress.end(), a[i]) - compress.begin() + 1;
		b[i] = lower_bound(compress.begin(), compress.end(), b[i]) - compress.begin() + 1;
	}
	N = compress.size();
	if(*min_element(b + 1, b + n + 1) == *max_element(b + 1, b + n + 1)){
		sub2::solve();
	}
	else if(n <= 5000){
		bool is_sub3 = true;
		for(int i = 2; i <= n; i++){
			if(a[i] < a[i - 1]){
				is_sub3 = false;
				break;
			}
		}
		if(is_sub3){
			sub3::solve();
		}
		else{
			sub156::solve();
		}
	}
	else{
		sub4::solve();
	}
}

Compilation message (stderr)

exam.cpp: In function 'int main()':
exam.cpp:128:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  128 |                 freopen(taskname".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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