Submission #397001

#	Time	Username	Problem	Language	Result	Execution time	Memory
397001		lyc	Three Friends (BOI14_friends)	C++14	100 / 100	14 ms	7084 KiB

friends

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

#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)

const int mxN = 2e6+5;

int N, cnt;
string S, a1, a2;

string solve() {
    int m = N/2, l = -1, r = m+1, ok;

    ok = 1;
    FOR(i,0,m-1){
        ok &= S[i] == S[i+m+1];
        if (ok) l = i;
        else break;
    }

    ok = 1;
    RFOR(i,m,0){
        ok &= S[i] == S[i+m];
        if (ok) r = i;
        else break;
    }

    TRACE(l _ r);
    if (l+2 >= r) return S.substr(m+1,N-m-1);
    return "";
}

int main() {
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);

    cin >> N >> S;

    a1 = solve();
    reverse(ALL(S));
    a2 = solve();
    reverse(ALL(a2));
    if (!SZ(a1) && !SZ(a2)) cout << "NOT POSSIBLE" << '\n';
    else if (SZ(a1) && SZ(a2) && a1 != a2) cout << "NOT UNIQUE" << '\n';
    else cout << (SZ(a1) ? a1 : a2) << '\n';
}

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