Submission #314538

#	Time	Username	Problem	Language	Result	Execution time	Memory
314538		Fidisk	Three Friends (BOI14_friends)	C++14	100 / 100	110 ms	52340 KiB

friends

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

#define oo 1e9
#define fi first
#define se second
#define sp(iiii) setprecision(iiii)
#define IO ios_base::sync_with_stdio(false); cin.tie(0)
#define ms(aaaa,xxxx) memset(aaaa,xxxx,sizeof(aaaa))
#define cntbit(xxxx) __builtin_popcount(xxxx)
#define getbit(xxxx,aaaa) ((xxxx>>(aaaa-1))&1)

typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<pair<int,int>,int> piii;
typedef pair<long long,long long> pll;
typedef pair<pair<long long,long long>,long long> plll;

const ll mod=1e9+7;
const ll base=361;

string s;
ll n,i,hashs[5000009],po[5000009],pos,type[5000009],cur;
bool ok;

ll get(ll x,ll y) {
    if (x>y) {
        return 0;
    }
    return (hashs[y]-hashs[x-1]*po[y-x+1]+mod*mod)%mod;
}

int main(){
    IO;
    //freopen("threefriend.inp","r",stdin);
//freopen("threefriend.out","w",stdout);
    cin>>n;
    cin>>s;
    //cout<<n<<'\n';
    //cout<<s<<'\n';
    if (n%2==0) {
        cout<<"NOT POSSIBLE";
        return 0;
    }
    s=" "+s;
    po[0]=1;
    for (i=1;i<=n;i++) {
        hashs[i]=(hashs[i-1]*base+s[i])%mod;
        po[i]=(po[i-1]*base)%mod;
    }
    for (i=1;i<=n;i++) {
        if (s[i]!=s[i-1]) {
            cur++;
        }
        type[i]=cur;
    }
    for (i=1;i<=n;i++) {
        if (i<=((n+1)/2)) {
            //cout<<1<<' '<<i-1<<' '<<(n+1)/2+1<<' '<<(n+1)/2+i-1<<' '<<i+1<<' '<<(n+1)/2<<' '<<(n+1)/2+i<<' '<<n<<'\n';
            if (get(1,i-1)==get((n+1)/2+1,(n+1)/2+i-1)&&get(i+1,(n+1)/2)==get((n+1)/2+i,n)) {
                if (ok&&type[i]!=type[pos]) {
                    cout<<"NOT UNIQUE";
                    return 0;
                }
                else {
                    ok=true;
                    pos=i;
                }
            }
        }
        else {
            //cout<<1<<' '<<i-(n+1)/2<<' '<<(n+1)/2<<' '<<i-1<<' '<<i-(n+1)/2+1<<' '<<(n+1)/2-1<<' '<<i+1<<' '<<n<<'\n';
            if (get(1,i-(n+1)/2)==get((n+1)/2,i-1)&&get(i-(n+1)/2+1,(n+1)/2-1)==get(i+1,n)) {
                if (ok&&type[i]!=type[pos]) {
                    cout<<"NOT UNIQUE";
                    return 0;
                }
                else {
                    ok=true;
                    pos=i;
                }
            }
        }
    }
    if (!ok) {
        cout<<"NOT POSSIBLE";
        return 0;
    }
    if (pos<=(n+1)/2) {
        for (i=(n+3)/2;i<=n;i++) {
            cout<<s[i];
        }
    }
    else {
        for (i=1;i<(n+1)/2;i++) {
            cout<<s[i];
        }
    }
}

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