oj.uz

Submission #869230

# Submission time Handle Problem Language Result Execution time Memory
869230 2023-11-03T15:38:19 Z Calico Necklace (Subtask 1-3) (BOI19_necklace1) C++17
85 / 85
 201 ms 524 KB 
#include <bits/stdc++.h>
using namespace std;

/*
	|--- S1 S2 ---|
	|--- T2 T1 ---|

	(T1 = S1, T2 = S2)

	Iterate through T-cut

	forward KMP through T1, backward KMP through T2
*/

vector<int> pi(const string& s) {
	vector<int> p(s.size());
	for (int i = 1; i < (int)s.size(); i++) {
		int g = p[i-1];
		while (g && s[i] != s[g]) g = p[g-1];
		p[i] = g + (s[i] == s[g]);
	}
	return p;
}

// finds the longest necklace, no reversal
tuple<int, int, int> solve(string &s, string &t) {
	int n = s.size(), m = t.size();

	int l = 0, a = 0, b = 0;
	for (int cut = 0; cut < m; cut++) {
		// T1 = [0, cut), T2 = [cut, m)

		vector<int> fBord(n), bBord(n); // S1, S2

		{ // forward kmp (T1)
			string s2 = t.substr(cut, m-cut);
			vector<int> kmp = pi(s2);

			int cur = 0;
			for (int i = 0; i < n; i++) {
				while (cur != 0 && s[i] != s2[cur]) {
					cur = kmp[cur-1];
				}
				if (s[i] == s2[cur]) {
					cur++;
				}
				fBord[i] = cur;
				if (cur == (int)s2.size()) {
					cur = kmp[cur-1];
				}
			}
		}

		if (cut > 0) { // backwards kmp (T2)
			string s2 = t.substr(0, cut);
			reverse(s2.begin(), s2.end());
			vector<int> kmp = pi(s2);

			int cur = 0;
			for (int i = n-1; i >= 0; i--) {
				while (cur != 0 && s[i] != s2[cur]) {
					cur = kmp[cur-1];
				}
				if (s[i] == s2[cur]) {
					cur++;
				}
				bBord[i] = cur;
				if (cur == (int)s2.size()) {
					cur = kmp[cur-1];
				}
			}
		}

		// find optimal cut position
		for (int i = 0; i < n; i++) {
			int mxlen = bBord[i];
			if (i > 0) mxlen += fBord[i-1];

			if (mxlen > l) {
				l = mxlen;
				a = (i > 0 ? i-fBord[i-1] : 0);
				b = cut - bBord[i];
			}
		}
	}

	return {l, a, b};
}

signed main() {
	ios::sync_with_stdio(0); cin.tie(0);

	string s, t; cin >> s >> t;
	int /*n = s.size(),*/ m = t.size();

	auto [l1, a1, b1] = solve(s, t);
	reverse(t.begin(), t.end());
	auto [l2, a2, b2] = solve(s, t); 
	b2 = m-(b2+l2-1)-1;

	if (l1 > l2) {
		cout << l1 << '\n' << a1 << ' ' << b1 << '\n';
	} else {
		cout << l2 << '\n' << a2 << ' ' << b2 << '\n';
	}

	return 0;
}

Subtask #1
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 348 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct

Subtask #2
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 348 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 4 ms 348 KB Output is correct
7 Correct 3 ms 348 KB Output is correct
8 Correct 3 ms 348 KB Output is correct
9 Correct 3 ms 348 KB Output is correct
10 Correct 3 ms 500 KB Output is correct
11 Correct 3 ms 492 KB Output is correct
12 Correct 3 ms 348 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 348 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 4 ms 348 KB Output is correct
7 Correct 3 ms 348 KB Output is correct
8 Correct 3 ms 348 KB Output is correct
9 Correct 3 ms 348 KB Output is correct
10 Correct 3 ms 500 KB Output is correct
11 Correct 3 ms 492 KB Output is correct
12 Correct 3 ms 348 KB Output is correct
13 Correct 187 ms 520 KB Output is correct
14 Correct 146 ms 344 KB Output is correct
15 Correct 201 ms 348 KB Output is correct
16 Correct 157 ms 524 KB Output is correct
17 Correct 107 ms 348 KB Output is correct
18 Correct 113 ms 516 KB Output is correct
19 Correct 131 ms 516 KB Output is correct
20 Correct 152 ms 516 KB Output is correct
21 Correct 159 ms 516 KB Output is correct