Submission #91722

#	Time	Username	Problem	Language	Result	Execution time	Memory
91722		Mercenary	Three Friends (BOI14_friends)	C++14	100 / 100	20 ms	10096 KiB

friends

#include<bits/stdc++.h>

using namespace std;
#define taskname "TEST"
#define pb	push_back
typedef long double ld;
typedef long long ll;
const int maxn = 2e6 + 5;
const int mod = 1e9 + 9;
const int base = 33;

int n;
string s;

string can(string need , int st , int en)
{
    string res = "";
    int it = 0;int ok = 1;
    for(int i = st ; i <= en && res.size() < n / 2 ; ++i)
    {
        if(need[it] == s[i])
            res.pb(s[i]) , ++it;
        else
        {
            if(ok == 0)return "-1";
            ok = 0;
        }
    }
    return res;
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	if(fopen(taskname".INP","r"))
        freopen(taskname".INP", "r",stdin) ,
        freopen(taskname".OUT", "w",stdout);
    cin >> n >> s;
    if(n % 2 == 0)return cout << "NOT POSSIBLE" , 0;
    s = " " + s;
    string res1 = can(s.substr(1,n/2),n/2+1,n);
    string res2 = can(s.substr(n/2+2,n/2),1,n/2+1);
    if(res1 == "-1" && res2 == "-1")cout << "NOT POSSIBLE";
    else if(res1 == "-1")cout << res2;
    else if(res2 == "-1")cout << res1;
    else if(res1 == res2)cout << res1;
    else cout << "NOT UNIQUE";
}

Compilation message (stderr)

friends.cpp: In function 'std::__cxx11::string can(std::__cxx11::string, int, int)':
friends.cpp:19:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = st ; i <= en && res.size() < n / 2 ; ++i)
                                 ~~~~~~~~~~~^~~~~~~
friends.cpp: In function 'int main()':
friends.cpp:37:44: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen(taskname".INP", "r",stdin) ,
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
         freopen(taskname".OUT", "w",stdout);
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
friends.cpp:37:44: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]

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