Submission #824785

#	Time	Username	Problem	Language	Result	Execution time	Memory
824785		QwertyPi	Three Friends (BOI14_friends)	C++14	100 / 100	42 ms	6432 KiB

friends

#include <bits/stdc++.h>
#define int long long
using namespace std;

const int MAXN = 2e6 + 11;

bool check(const string& s, const string& t){
	int si = 0;
	for(auto c : t){
		while(si < s.size() && s[si] != c){
			si++;
		}
		if(si >= s.size() || s[si] != c) return false;
		si++;
	}
	for(auto c : t){
		while(si < s.size() && s[si] != c){
			si++;
		}
		if(si >= s.size() || s[si] != c) return false;
		si++;
	}
	return true;
}

int32_t main() {
	int n; cin >> n;
	string s; cin >> s;
	if(n % 2 == 0){
		cout << "NOT POSSIBLE" << endl;
		return 0;
	}

	string t1 = s.substr(0, n / 2);
	string t2 = s.substr(n / 2 + 1);
	bool ok1 = check(s, t1);
	bool ok2 = check(s, t2);

	if(ok1 && ok2 && t1 != t2){
		cout << "NOT UNIQUE" << endl;
	}else if(ok1){
		cout << t1 << endl;
	}else if(ok2){
		cout << t2 << endl;
	}else{
		cout << "NOT POSSIBLE" << endl;
	}
}

Compilation message (stderr)

friends.cpp: In function 'bool check(const string&, const string&)':
friends.cpp:10:12: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |   while(si < s.size() && s[si] != c){
      |         ~~~^~~~~~~~~~
friends.cpp:13:9: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |   if(si >= s.size() || s[si] != c) return false;
      |      ~~~^~~~~~~~~~~
friends.cpp:17:12: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |   while(si < s.size() && s[si] != c){
      |         ~~~^~~~~~~~~~
friends.cpp:20:9: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |   if(si >= s.size() || s[si] != c) return false;
      |      ~~~^~~~~~~~~~~

• Subtask 1: 35 / 35
• Subtask 2: 65 / 65