Submission #420332

#	Time	Username	Problem	Language	Result	Execution time	Memory
420332		abdzag	Necklace (Subtask 1-3) (BOI19_necklace1)	C++17	25 / 85	1570 ms	95548 KiB

necklace

#include<bits/stdc++.h>
#include<unordered_map>
#define rep(i,a,b) for(int i=int(a);i<int(b);i++)
#define rrep(i,a,b) for(int i=int(a);i>int(b);i--)
#define trav(a,v) for(auto& a: v)
#define sz(v) v.size()
#define all(v) v.begin(),v.end()
#define vi vector<int>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const long long inf = 1e15;
vector<ull> suffix(1e5);
vector<ull> suffix2(1e5);
vector<ull> suffix3(1e5);
vector<ull> powers(1e5);
ll n;
ull getS(vector<ull>& v,ll start, ll end) {
	return v[start] - (v[end] * powers[end-start]);
}
int main() {
	cin.sync_with_stdio(false);
	vector<ull> primes = { 43,47,53,59,61,67,71,73,79,83,89,97,101,103,107 };
	string a,b;
	cin >> a >> b;
	n = a.size();
	ull c = primes[rand() % primes.size()];
	powers[0] = 1;
	rep(i, 1, 1e5)powers[i] = powers[i - 1] * c;
	rrep(i, a.size() - 1, -1)suffix[i] = a[i] + c * suffix[i + 1];
	rrep(i, b.size() - 1, -1)suffix2[i] = b[i] + c * suffix2[i + 1];
	reverse(all(a));
	rrep(i, a.size() - 1, -1)suffix3[i] = a[i] + c * suffix3[i + 1];

	map<ull, int> mp;
	rep(i, 0, a.size()+1) {
		rep(j, i + 1, a.size() + 1) {
			mp[getS(suffix, i, j)] = i+1;
			mp[getS(suffix3, i, j)] = a.size()-i-(j-i)+1;
		}
	}
	ll l = 1, r = a.size();
	ll ans = 0;
	ll pos1, pos2;
	rep (mid,0,b.size()) {
		int done = 0;
		rep(i, 0, b.size() - mid + 1) {
			ull val = getS(suffix2, i, i + mid);
			rep(j, 0, mid) {
				val -= getS(suffix2, i+mid - j - 1, i+mid - j) * powers[mid-1];
				val *= c;
				val += getS(suffix2, i+mid - j - 1, i+mid - j);
				if (mp[val]) {
					done = mp[val];
					pos2 = i;
					break;
				}
			}
		}
		if (done) {
			ans = mid;
			pos1 = done;
		}
	}
	cout << ans << endl;
	if(ans)cout << pos1-1 << " " << pos2 << endl;
	return 0;
}

Compilation message (stderr)

necklace.cpp: In function 'int main()':
necklace.cpp:43:5: warning: unused variable 'l' [-Wunused-variable]
   43 |  ll l = 1, r = a.size();
      |     ^
necklace.cpp:43:12: warning: unused variable 'r' [-Wunused-variable]
   43 |  ll l = 1, r = a.size();
      |            ^

• Subtask 1: 25 / 25
• Subtask 2: 0 / 20
• Subtask 3: 0 / 40