Submission #125437

#	Time	Username	Problem	Language	Result	Execution time	Memory
125437		wasyl	Three Friends (BOI14_friends)	C++11	100 / 100	19 ms	9112 KiB

friends

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

constexpr int nax = 2e6 + 1;

int n;
string s;

pair< bool, string > spr(const string& a, const string& b)
{
    //cerr << a << ' ' << b << ' ';
    int pt = 0;
    for (int i = 0; i < a.size(); ++i)
        if (pt < b.size() and a[i] == b[pt])
            ++pt;
    //cerr << pt << '\n';

    if (pt < b.size()) return {false, ""};
    else return {true, b};
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> s;

    if (n % 2 == 0)
        return cout << "NOT POSSIBLE" << '\n', 0;

    int d = (n - 1) / 2;
    pair< bool, string > p, q;
    p = spr(s.substr(0, d + 1), s.substr(d + 1, d));
    q = spr(s.substr(d, d + 1), s.substr(0, d));

    if (p.first and q.first and (p.second != q.second))
        return cout << "NOT UNIQUE" << '\n', 0;
    if (not p.first) swap(p, q);
    if (not p.first)
        cout << "NOT POSSIBLE" << '\n';
    else
        cout << p.second << '\n';
}

Compilation message (stderr)

friends.cpp: In function 'std::pair<bool, std::__cxx11::basic_string<char> > spr(const string&, const string&)':
friends.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); ++i)
                     ~~^~~~~~~~~~
friends.cpp:14:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (pt < b.size() and a[i] == b[pt])
             ~~~^~~~~~~~~~
friends.cpp:18:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (pt < b.size()) return {false, ""};
         ~~~^~~~~~~~~~

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