Submission #432351

#	Time	Username	Problem	Language	Result	Execution time	Memory
432351		cpp219	Three Friends (BOI14_friends)	C++14	100 / 100	35 ms	10052 KiB

friends

#pragma GCC optimization "O2"
#pragma GCC optimization "unroll-loop"
#pragma GCC target ("avx2")

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define fs first
#define sc second
using namespace std;
const ll N = 2e6 + 9;
const ll mod = 1e9 + 7;
const ll base = 31;
typedef pair<ll,ll> LL;
string s;
string p,q;
vector<string> ans;
ll n;

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    #define task "tst"
    if (fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        //freopen(task".out", "w", stdout);
    }
    cin>>n>>s; s = " " + s;
    if (n%2 == 0) return cout<<"NOT POSSIBLE",0;
    /// X to head
    ll pos = 1;

    while(pos <= n/2 && s[pos] == s[pos + n/2]) pos++;
    for(ll i = 1;i <= n/2;i++) p += s[i];
    for (ll i = n/2 + 1;i <= n;i++) if (i != pos + n/2) q += s[i];
    if (p == q) ans.push_back(p);
    p = ""; q = ""; pos = 1;

    while(pos <= n/2&&s[pos] == s[pos + 1 + n/2]) pos++;
    for(ll i = 1;i <= n/2 + 1;i++) if (i != pos) p += s[i];
    for (ll i = n/2 + 2;i <= n;i++) q += s[i];
    if (p == q) ans.push_back(p);

    if (!ans.size()) cout<<"NOT POSSIBLE";
    else if (ans.size() == 1) cout<<ans[0];
    else{
        if (ans[0] != ans[1]) cout<<"NOT UNIQUE";
        else cout<<ans[0];
    }
}

Compilation message (stderr)

friends.cpp:1: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    1 | #pragma GCC optimization "O2"
      | 
friends.cpp:2: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    2 | #pragma GCC optimization "unroll-loop"
      | 
friends.cpp: In function 'int main()':
friends.cpp:25:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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