Submission #831147

#	Time	Username	Problem	Language	Result	Execution time	Memory
831147		pera	Exam (eJOI20_exam)	C++17	62 / 100	97 ms	28092 KiB

exam

#include<bits/stdc++.h>
using namespace std;
 
#define int long long
 
const int N = 2e5 + 1;

vector<int> t(4 * N) , x(4 * N) , a(N) , b(N) , L(N) , R(N);
map<int , int> M;

void up(int v , int l ,int r , int p , int x){
	if(l == r){
		t[v] = x;
		return;
	}
	int m = (l + r) / 2;
	if(p <= m) up(v * 2 , l , m , p , x);
	else up(v * 2 + 1 , m + 1 , r , p , x);
	t[v] = max(t[v * 2] , t[v * 2 + 1]);
}

int g(int v , int l , int r , int L , int R){
	if(l > r || r < L || l > R) return 0;
	if(L <= l && r <= R) return t[v];
	int m = (l + r) / 2;
	return max(g(v * 2 , l , m , L , R) , g(v * 2 + 1 , m + 1 , r , L , R));
}
 
main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	int n , oK = 1;cin >> n;
	for(int i = 1;i <= n;i ++){
		cin >> a[i];
		M[a[i]] = i;
	}
	for(int i = 1;i <= n;i ++){
		cin >> b[i];
		if(i != 1) oK &= (b[i] == b[i - 1]);
	}
	for(int i = 1;i <= n;i ++){
		L[i] = i - 1;
		while(L[i] && a[L[i]] <= a[i]) L[i] = L[L[i]];
	}
	for(int i = n;i >= 1;i --){
		R[i] = i + 1;
		while(R[i] != n + 1 && a[R[i]] <= a[i]) R[i] = R[R[i]];
	}
	if(oK){
		int c = 0;
		for(int i = 1;i <= n;i ++){
			int cc = 0 , k = 0;
			while(a[i] <= b[i] && i <= n){
				if(a[i] == b[i]) k = 1;
				++ cc , ++ i; 
			}
			if(k) c += cc;
		}
		cout << c << endl;
		return 0;
	}
	oK = 1;
	for(int i = 2;i <= n;i ++){
		oK &= (a[i] > a[i - 1]);
	}
	if(oK){
		vector<int> dp(n + 1);
		dp[1] = (a[1] == b[1]);
		for(int i = 2;i <= n;i ++){
			int q = 0;
			for(int j = i;j >= 1;j --){
				q += (a[i] == b[j]);
				dp[i] = max(dp[i] , q + dp[j - 1]);
			}
			for(int j = 1;j <= i;j ++){
				dp[j] = max(dp[j] , dp[j - 1] + (a[i] == b[j]));
			}
		}
		cout << *max_element(dp.begin() , dp.end()) << endl;
		return 0;
	}
	if(M.size() == n){
		vector<int> ans(n + 1);
		for(int i = 1;i <= n;i ++){
			if(M.find(b[i]) != M.end()){
				int p = M[b[i]];
				if(L[p] < i && i < R[p]){
					ans[i] = g(1 , 1 , n , 1 , p) + 1;
					up(1 , 1 , n , p , ans[i]);
				}
			}
		}
		cout << *max_element(ans.begin() , ans.end()) << endl;
		return 0;
	}
	assert(n <= 5000);
	vector<vector<int>> dp(n + 1 , vector<int>(n + 1));
	for(int i = 1;i <= n;i ++){
		for(int j = 1;j <= n;j ++){
			if(a[i] == b[j] && L[i] < j && j < R[j]){
				dp[i][j] = dp[i][j - 1] + 1;
			}
			dp[i][j] = max({dp[i][j] , dp[i - 1][j] , dp[i][j - 1]});
		}
	}
	cout << dp[n][n] << endl;
}

Compilation message (stderr)

exam.cpp:29:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   29 | main(){
      | ^~~~
exam.cpp: In function 'int main()':
exam.cpp:82:14: warning: comparison of integer expressions of different signedness: 'std::map<long long int, long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   82 |  if(M.size() == n){
      |     ~~~~~~~~~^~~~

• Subtask 1: 14 / 14
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 23 / 23
• Subtask 5: 0 / 16
• Subtask 6: 0 / 22