oj.uz

Submission #291292

# Submission time Handle Problem Language Result Execution time Memory
291292 2020-09-05T05:07:15 Z eggag32 Three Friends (BOI14_friends) C++17
100 / 100
 232 ms 96408 KB 
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int, int> pi;
#define debug(x) cerr << #x << ": " << x << endl;
#define debug2(x, y) debug(x) debug(y);
#define repn(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
#define rep(i, a) for(int i = 0; i < (int)(a); i++)
#define all(v) v.begin(), v.end() 
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define sq(x) ((x) * (x))

template<class T> T gcd(T a, T b){ return ((b == 0) ? a : gcd(b, a % b)); }

pair<ll, ll> hsh[2000005];
ll inv1[2000005], inv2[2000005];
ll p = 349, p1 = 179, m = 1e9 + 7, m1 = 1e9 + 9;

void computeHashes(string s){
	ll hash_value1 = 0, hash_value2 = 0;
	ll p_pow1 = 1, p_pow2 = 1;
	int cnt = 0;
	for(char c : s){
		hash_value1 = (hash_value1 + (c - '0' + 1) * p_pow1) % m;
		hash_value2 = (hash_value2 + (c - '0' + 1) * p_pow2) % m1;
		hsh[cnt] = mp(hash_value1, hash_value2);
		cnt++;
		p_pow1 = (p_pow1 * p) % m;
		p_pow2 = (p_pow2 * p1) % m1;
	}
}

ll mypow(ll a, ll p, ll MOD){
	if(p == 0) return 1;
	if(p == 1) return (a % MOD);
	if(p & 1) return ((a % MOD) * (mypow(a, p - 1, MOD) % MOD)) % MOD;
	ll x = mypow(a, p / 2, MOD) % MOD;
	return (x * x) % MOD;
}

void computeInvs(){
	inv1[0] = 1;
	for(int j = 1; j <= 2000000; j++){
      		if(j == 1) inv1[j] = mypow(p, m - 2, m);
		else inv1[j] = (inv1[j - 1] * inv1[1]) % m;
	}
	inv2[0] = 1;
	for(int j = 1; j <= 2000000; j++){
      		if(j == 1) inv2[j] = mypow(p1, m1 - 2, m1);
		else inv2[j] = (inv2[j - 1] * inv2[1]) % m1;
	}
}
 
pair<ll, ll> comp_hs(int i, int j){
	ll hs1 = ((hsh[j].fi - (i ? hsh[i - 1].fi : 0)) + m) % m;
	ll hs2 = ((hsh[j].se - (i ? hsh[i - 1].se : 0)) + m1) % m1;
	(hs1 *= inv1[i]) %= m;
	(hs2 *= inv2[i]) %= m1;
	return mp(hs1, hs2);
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	//freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
	int n;
	cin >> n;
	string s;
	cin >> s;
	if(n % 2 == 0){
		cout << "NOT POSSIBLE" << endl;
		return 0;
	}
	char ch = 'z';
	vi cnt(30, 0);
	rep(i, n) cnt[s[i] - 'A']++;
	rep(i, 30) if(cnt[i] & 1) ch = (char)('A' + i);
	assert(ch != 'z');
	set<pair<ll, ll>> st;
	vi pref(n / 2 + 1, 0), suf(n / 2 + 1, 0);
	int len = n / 2;
	rep(i, n / 2 + 1){
		if(s[i] != s[i + len + 1]) break;
		else pref[i] = 1;
	}
	for(int i = n / 2; i >= 1; i--){
		if(s[i] != s[i + len]) break;
		else suf[i] = 1;
	}
	string ans = "";
	computeInvs();
	computeHashes(s);	
	repn(i, 1, n / 2) if(s[i] == ch){
		if(pref[i - 1] && suf[i + 1]){
			//string c = s.substr(n / 2 + 1, len);
			//st.insert(c);
			if(!ans.size()){
				ans = s.substr(n / 2 + 1, len);
			}
			st.insert(comp_hs(n / 2 + 1, n / 2 + 1 + (len - 1)));
			if(st.size() > 1){
				cout << "NOT UNIQUE" << endl;
				return 0;
			}
		}
	}
	vi pref1(n, 0), suf1(n, 0);
	for(int i = n - 1; i >= n / 2; i--){
		if(s[i] !=  s[i - len - 1]) break;
		else suf1[i] = 1;
	}
	repn(i, n / 2, n){
		if(s[i] !=  s[i - len]) break;
		else pref1[i] = 1;
	}
	repn(i, n / 2 + 1, n) if(s[i] == ch){
		if(pref1[i - 1] && suf1[i + 1]){
			//string c = s.substr(0, len);
			//st.insert(c);
			st.insert(comp_hs(0, len - 1));
			if(!ans.size()){
				ans = s.substr(0, len);
			}
			if(st.size() > 1){
				cout << "NOT UNIQUE" << endl;
				return 0;
			}
		}
	}
	string a1 = s.substr(1, len), a2 = s.substr(len + 1, len);
	if(a1 == a2){
		st.insert(comp_hs(1, len));
		if(!ans.size()) ans = a1;
	}
	a1 = s.substr(0, len), a2 = s.substr(len + 1, len);
	if(a1 == a2){
		st.insert(comp_hs(0, len - 1));
		if(!ans.size()) ans = a1;
	}
	a1 = s.substr(0, len), a2 = s.substr(len, len);
	if(a1 == a2){
		st.insert(comp_hs(0, len - 1));
		if(!ans.size()) ans = a1;
	}
	if(!st.size()) cout << "NOT POSSIBLE" << endl;
	else if(st.size() == 1) cout << ans << endl;
	else cout << "NOT UNIQUE" << endl;
	return 0;
}
/*
Things to look out for:
	- Integer overflows
	- Array bounds
	- Special cases
Be careful!
*/

Subtask #1
35.0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 71 ms 31612 KB Output is correct
2 Correct 72 ms 31608 KB Output is correct
3 Correct 68 ms 31608 KB Output is correct
4 Correct 72 ms 31624 KB Output is correct
5 Correct 69 ms 31608 KB Output is correct
6 Correct 70 ms 31608 KB Output is correct
7 Correct 69 ms 31644 KB Output is correct
8 Correct 70 ms 31612 KB Output is correct
9 Correct 70 ms 31736 KB Output is correct
10 Correct 69 ms 31608 KB Output is correct
11 Correct 70 ms 31696 KB Output is correct
12 Correct 69 ms 31608 KB Output is correct
13 Correct 69 ms 31608 KB Output is correct
14 Correct 69 ms 31608 KB Output is correct
15 Correct 68 ms 31608 KB Output is correct
16 Correct 69 ms 31608 KB Output is correct
17 Correct 69 ms 31608 KB Output is correct
18 Correct 68 ms 31608 KB Output is correct
19 Correct 68 ms 31608 KB Output is correct
20 Correct 68 ms 31608 KB Output is correct
21 Correct 70 ms 31736 KB Output is correct
22 Correct 73 ms 31608 KB Output is correct
23 Correct 68 ms 31608 KB Output is correct
24 Correct 1 ms 384 KB Output is correct
25 Correct 0 ms 384 KB Output is correct
26 Correct 1 ms 384 KB Output is correct
27 Correct 68 ms 31608 KB Output is correct
28 Correct 76 ms 31608 KB Output is correct
29 Correct 70 ms 31608 KB Output is correct
30 Correct 71 ms 31608 KB Output is correct
31 Correct 72 ms 31608 KB Output is correct
32 Correct 69 ms 31608 KB Output is correct
33 Correct 73 ms 31608 KB Output is correct
34 Correct 70 ms 31608 KB Output is correct
35 Correct 66 ms 31612 KB Output is correct
36 Correct 74 ms 31608 KB Output is correct
37 Correct 77 ms 31680 KB Output is correct
38 Correct 68 ms 31608 KB Output is correct
39 Correct 70 ms 31608 KB Output is correct
40 Correct 67 ms 31736 KB Output is correct
41 Correct 72 ms 31608 KB Output is correct
42 Correct 66 ms 31608 KB Output is correct
43 Correct 66 ms 31608 KB Output is correct
44 Correct 73 ms 31736 KB Output is correct
45 Correct 66 ms 31736 KB Output is correct
46 Correct 73 ms 31736 KB Output is correct
47 Correct 67 ms 31736 KB Output is correct
48 Correct 68 ms 31864 KB Output is correct
49 Correct 1 ms 384 KB Output is correct
50 Correct 70 ms 31736 KB Output is correct
51 Correct 68 ms 31716 KB Output is correct
52 Correct 68 ms 31736 KB Output is correct
53 Correct 71 ms 31736 KB Output is correct
54 Correct 71 ms 31736 KB Output is correct

Subtask #2
65.0 / 65.0

# Verdict Execution time Memory Grader output
1 Correct 173 ms 96408 KB Output is correct
2 Correct 169 ms 96252 KB Output is correct
3 Correct 170 ms 96264 KB Output is correct
4 Correct 170 ms 96244 KB Output is correct
5 Correct 179 ms 96304 KB Output is correct
6 Correct 9 ms 4388 KB Output is correct
7 Correct 232 ms 96240 KB Output is correct
8 Correct 161 ms 88896 KB Output is correct
9 Correct 164 ms 88888 KB Output is correct
10 Correct 158 ms 89788 KB Output is correct
11 Correct 150 ms 83900 KB Output is correct
12 Correct 69 ms 31596 KB Output is correct
13 Correct 69 ms 31600 KB Output is correct
14 Correct 69 ms 31608 KB Output is correct
15 Correct 68 ms 31608 KB Output is correct
16 Correct 68 ms 31608 KB Output is correct
17 Correct 69 ms 31584 KB Output is correct
18 Correct 69 ms 31608 KB Output is correct
19 Correct 68 ms 31612 KB Output is correct
20 Correct 67 ms 31608 KB Output is correct
21 Correct 67 ms 31608 KB Output is correct
22 Correct 68 ms 31608 KB Output is correct
23 Correct 67 ms 31608 KB Output is correct
24 Correct 70 ms 31608 KB Output is correct
25 Correct 69 ms 31608 KB Output is correct
26 Correct 67 ms 31608 KB Output is correct
27 Correct 69 ms 31608 KB Output is correct
28 Correct 68 ms 31608 KB Output is correct
29 Correct 69 ms 31608 KB Output is correct
30 Correct 68 ms 31608 KB Output is correct
31 Correct 68 ms 31608 KB Output is correct
32 Correct 68 ms 31612 KB Output is correct
33 Correct 69 ms 31608 KB Output is correct
34 Correct 73 ms 31608 KB Output is correct
35 Correct 0 ms 384 KB Output is correct
36 Correct 1 ms 384 KB Output is correct
37 Correct 1 ms 384 KB Output is correct
38 Correct 68 ms 31608 KB Output is correct
39 Correct 70 ms 31608 KB Output is correct
40 Correct 69 ms 31612 KB Output is correct
41 Correct 69 ms 31608 KB Output is correct
42 Correct 69 ms 31608 KB Output is correct
43 Correct 69 ms 31608 KB Output is correct
44 Correct 70 ms 31608 KB Output is correct
45 Correct 69 ms 31608 KB Output is correct
46 Correct 69 ms 31608 KB Output is correct
47 Correct 69 ms 31608 KB Output is correct
48 Correct 69 ms 31608 KB Output is correct
49 Correct 68 ms 31608 KB Output is correct
50 Correct 69 ms 31608 KB Output is correct
51 Correct 69 ms 31608 KB Output is correct
52 Correct 68 ms 31664 KB Output is correct
53 Correct 69 ms 31644 KB Output is correct
54 Correct 69 ms 31648 KB Output is correct