Submission #563416

#	Time	Username	Problem	Language	Result	Execution time	Memory
563416		zaneyu	Three Friends (BOI14_friends)	C++14	100 / 100	34 ms	9232 KiB

friends

/*input
9
ABABABABA
*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
//order_of_key #of elements less than x
// find_by_order kth element
typedef long long int ll;
 
#define ld long double
#define pii pair<int,int>
typedef tree<pii, null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
const ll maxn=2e5+5;
const ll maxlg=__lg(maxn)+2;
const ll INF64=4e18;
const int MOD=1e9+7;
const int INF=0x3f3f3f3f;
const ld PI=acos(-1);
const ld eps=1e-9;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#define GET_POS(c,x) (lower_bound(c.begin(),c.end(),x)-c.begin())+1
template<typename T1,typename T2>
ostream& operator<<(ostream& out,pair<T1,T2> P){
    out<<P.f<<' '<<P.s;
    return out;
}
template<typename T>
ostream& operator<<(ostream& out,vector<T> V){
    REP(i,sz(V)) out<<V[i]<<((i!=sz(V)-1)?"\n":"");
    return out;
}
ll mult(ll a,ll b){
    if(a<0) a+=MOD;
    return (a*b)%MOD;
}
ll mypow(ll a,ll b){
    if(b<=0) return 1;
    ll res=1LL;
    while(b){
        if(b&1) res=mult(res,a);
        a=mult(a,a);
        b>>=1;
    }
    return res;
}
bool mtch(string a,string b){
    int p=0;
    REP(i,sz(a)){
        while(p<sz(b) and b[p]!=a[i]) ++p;
        if(p==sz(b)){
            return false;
        }
        ++p;
    }
    return true;
}
int32_t main(){
    ios::sync_with_stdio(false),cin.tie(0);
    int n;
    cin>>n;
    string s;
    cin>>s;
    set<string> ss;
    if(n%2==0){
        cout<<"NOT POSSIBLE\n";
        return 0;
    }
    string a="",b="";
    REP(i,n/2) a.pb(s[i]);
    REP(i,n/2+1) b.pb(s[i+n/2]);
    if(mtch(a,b)) ss.insert(a);
    a="",b="";
    REP(i,n/2+1) a.pb(s[i]);
    REP(i,n/2) b.pb(s[i+n/2+1]);
    if(mtch(b,a)) ss.insert(b);
    if(sz(ss)==2){
        cout<<"NOT UNIQUE\n";
    }
    else if(!sz(ss)){
        cout<<"NOT POSSIBLE\n";
    }
    else{
        cout<<(*ss.begin());
    }
}

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