Submission #57713

#	Time	Username	Problem	Language	Result	Execution time	Memory
57713		ksun48	Security Gate (JOI18_security_gate)	C++14	12 / 100	5009 ms	1008 KiB

securitygate

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

const LL MOD = 1000000007;

LL check(string s){
	vector<int> psums(1,0);
	for(int j = 0; j < s.size(); j++){
		if(s[j] == '('){
			psums.push_back(psums[psums.size() - 1] + 1);
		} else {
			psums.push_back(psums[psums.size() - 1] - 1);			
		}
	}
	int laste = psums.size() - 1;
	while(laste > 0 && psums[laste-1] >= psums[psums.size()-1]){
		laste--;
	}
	map<int,vector<int> > endlists;
	for(int j = laste; j <= psums.size() - 1; j++){
		endlists[psums[j]].push_back(j);
	}
	int a = psums[psums.size() - 1] / 2;
	for(int j = 0; j < psums.size(); j++){
		if(psums[j] < 0) break;
		int need = psums[j] + a;
		vector<int>& z = endlists[need];
		int idx = lower_bound(z.begin(), z.end(), j) - z.begin();
		if(idx >= z.size()) continue;
		int e = z[idx];
		// check if all elements in [j,e] are <= 
		int ok = 1;
		for(int i = j; i <= e; i++){
			if(psums[i] > 2 * psums[j]){
				ok = 0;
				break;
			}
		}
		if(ok){
			return 1;
		}
	}
	return 0;
}

LL cnt(string s, int idx){
	if(idx == s.size()) return check(s);
	if(s[idx] != 'x'){
		return cnt(s, idx + 1);
	}
	string s1 = s;
	string s2 = s;
	s1[idx] = '(';
	s2[idx] = ')';
	return (cnt(s1, idx + 1) + cnt(s2, idx + 1)) % MOD;
}
int main(){
	int n;
	string s;
	cin >> n >> s;
	if(n % 2 == 1){
		cout << 0 << '\n';
		return 0;
	}
	cout << cnt(s, 0) << '\n';
}

Compilation message (stderr)

securitygate.cpp: In function 'LL check(std::__cxx11::string)':
securitygate.cpp:9:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j = 0; j < s.size(); j++){
                 ~~^~~~~~~~~~
securitygate.cpp:21:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j = laste; j <= psums.size() - 1; j++){
                     ~~^~~~~~~~~~~~~~~~~~~
securitygate.cpp:25:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j = 0; j < psums.size(); j++){
                 ~~^~~~~~~~~~~~~~
securitygate.cpp:30:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(idx >= z.size()) continue;
      ~~~~^~~~~~~~~~~
securitygate.cpp: In function 'LL cnt(std::__cxx11::string, int)':
securitygate.cpp:48:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(idx == s.size()) return check(s);
     ~~~~^~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 8 / 8
• Subtask 3: 0 / 18
• Subtask 4: 0 / 43
• Subtask 5: 0 / 27