Submission #58873

#	Time	Username	Problem	Language	Result	Execution time	Memory
58873		SpeedOfMagic	Three Friends (BOI14_friends)	C++17	0 / 100	209 ms	53888 KiB

friends

/** MIT License Copyright (c) 2018 Vasilyev Daniil **/
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
template<typename T> using v = vector<T>;
#define int long long
typedef string str;
typedef vector<int> vint;
#define rep(a, l, r) for(int a = (l); a < (r); a++)
#define pb push_back
#define sz(a) ((int) a.size())
const long long inf = 4611686018427387903; //2^62 - 1
#if 0  //FileIO
const string fileName = "";
ifstream fin ((fileName == "" ? "input.txt"  : fileName + ".in" ));
ofstream fout((fileName == "" ? "output.txt" : fileName + ".out"));
#define get fin>>
#define put fout<<
#else
#define get cin>>
#define put cout<<
#endif
#define eol put endl
void read() {}     template<typename Arg,typename... Args> void read (Arg& arg,Args&... args){get (arg)     ;read(args...) ;}
void print(){}     template<typename Arg,typename... Args> void print(Arg  arg,Args...  args){put (arg)<<" ";print(args...);}
void debug(){eol;} template<typename Arg,typename... Args> void debug(Arg  arg,Args...  args){put (arg)<<" ";debug(args...);}
int getInt(){int a; get a; return a;}
//code goes here
const long long mod2 = 2000001881;
const long long base = 29;
const char startingLetter = 'A'; //starting letter of the alphabet

long long hashChar(char c){
    return c - startingLetter + 1;
}

long long hashStr(long long prevHash, char curChar, long long mod = mod2) {
    return ((prevHash * base) % mod + hashChar(curChar)) % mod;
}

long long hashStr(string& s) {
    long long res = 0;

    for(char i : s)
        res = hashStr(res, i);

    return res;
}

const int mod = mod2;

const int N = 2e6 + 1;
int powOfBase[N], invPowOfBase[N];

void run() {
    int n;
    get n;
    str u;
    get u;

    powOfBase[0] = 1;
    rep(i, 1, n + 1)
        powOfBase[i] = (base * powOfBase[i - 1]) % mod;

    str left = "", right = "";
    rep(i, 0, n / 2 + 1)
        left += u[i];

    rep(i, n / 2 + 1, n)
        right += u[i];
        
    vint ans;
    rep(z, 0, 2) {
        vint hshLeft, hshRight;
        hshLeft.pb(hashChar(left[0]));
        rep(i, 1, sz(left)) {
            int d = hshLeft.back();
            hshLeft.pb(hashStr(d, left[i]));
        }
        
        hshRight.pb(hashChar(right[0]));
        rep(i, 1, sz(right)) {
            int d = hshRight.back();
            hshRight.pb(hashStr(d, right[i]));
        }
    
        if (z) {
            //debug(sz(hshRight), right, sz(hshLeft), left);
            rep(i, 0, sz(right)) {
                int resultHash = hshRight.back();
                int offset = sz(right) - (i + 1);
                resultHash = ((resultHash - (powOfBase[offset] * hshRight[i]) % mod) % mod + mod) % mod;
                
                if (i)
                    resultHash = (resultHash + (powOfBase[offset] * hshRight[i - 1]) % mod) % mod;
                if (resultHash == hshLeft.back())
                    ans.pb(i + sz(left));
                
            }
        } else {
            rep(i, 0, sz(left)) {
                int resultHash = hshLeft.back();
                int offset = sz(left) - (i + 1);
                resultHash = ((resultHash - (powOfBase[offset] * hshLeft[i]) % mod) % mod + mod) % mod;
                if (i)
                    resultHash = (resultHash + (powOfBase[offset] * hshLeft[i - 1]) % mod) % mod;
                
                //debug(i, resultHash, hshRight.back());
                if (resultHash == hshRight.back())
                    ans.pb(i);
            }
        }
        
        if (z)
            break;
            
        right = left.back() + right;
        left.pop_back();
    }
    //debug(ans[0]);
    if (sz(ans) == 0)
        put "NOT POSSIBLE";
    else if (sz(ans) == 1) {
        rep(i, 0, n / 2)
            if (i != ans[0])
                put u[i];
            else
                n++;
    
    } else
        put "NOT UNIQUE";
}

int32_t main() {srand(time(0)); ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); put fixed; put setprecision(15); run(); return 0;}

• Subtask 1: 0 / 35
• Subtask 2: 0 / 65