Submission #1253845

#	Time	Username	Problem	Language	Result	Execution time	Memory
1253845		TIN	Triple Peaks (IOI25_triples)	C++20	41.53 / 100	55 ms	1956 KiB

triples

#include "triples.h"
#include <algorithm>
#include <set>

long long count_triples(std::vector<int> H) {
	int N = (int) H.size();
	if (N <= 100) {
		long long ans = 0;
		for (int i = 0; i < N; i++) {
			for (int j = i + 1; j < N; j++) {
				for (int k = j + 1; k < N; k++) {
					if (H[i] == j - i && H[j] == k - j && H[k] == k - i) ++ans;
					else if (H[i] == j - i && H[k] == k - j && H[j] == k - i) ++ans;
					else if (H[j] == j - i && H[i] == k - j && H[k] == k - i) ++ans;
					else if (H[j] == j - i && H[k] == k - j && H[i] == k - i) ++ans;
					else if (H[k] == j - i && H[i] == k - j && H[j] == k - i) ++ans;
					else if (H[k] == j - i && H[j] == k - j && H[i] == k - i) ++ans;
				}
			}
		}
		return ans;
	}
	int mx = 0;
	for (int i = 0; i < N; i++) mx = std::max(mx, H[i]);
	if (mx <= 10) {
		long long ans = 0;
		for (int i = 0; i < N; i++) {
			for (int j = i + 1; j < std::min(N, i + mx); j++) {
				for (int k = j + 1; k < std::min(N, j + mx); k++) {
					if (H[i] == j - i && H[j] == k - j && H[k] == k - i) ++ans;
					else if (H[i] == j - i && H[k] == k - j && H[j] == k - i) ++ans;
					else if (H[j] == j - i && H[i] == k - j && H[k] == k - i) ++ans;
					else if (H[j] == j - i && H[k] == k - j && H[i] == k - i) ++ans;
					else if (H[k] == j - i && H[i] == k - j && H[j] == k - i) ++ans;
					else if (H[k] == j - i && H[j] == k - j && H[i] == k - i) ++ans;
				}
			}
		}
		return ans;
	}
	if (N <= 2000) {
		long long ans = 0;
		std::set<int> s;
		for (int k = 0; k < N; k++) {
			for (int i = 0; i < k; i++) {
				s.clear();
				int j;
				// i < j < k
				// H[i] = j - i
				j = i + H[i];
				if (i < j && j < k) {
					if (H[i] == j - i && H[j] == k - j && H[k] == k - i) ++ans, s.insert(j);
					else if (H[i] == j - i && H[k] == k - j && H[j] == k - i) ++ans, s.insert(j);
				}
				// H[i] = k - j
				j = k - H[i];
				if (i < j && j < k && s.find(j) == s.end()) {
					if (H[j] == j - i && H[i] == k - j && H[k] == k - i) ++ans, s.insert(j);
					else if (H[k] == j - i && H[i] == k - j && H[j] == k - i) ++ans, s.insert(j);
				}
				// H[i] = k - i
				if (i + H[i] == k) {
					// H[k] = k - j
					j = k - H[k];
					if ((i < j && j < k) && (H[j] == j - i) && (s.find(j) == s.end())) ++ans, s.insert(j);
					// H[k] = j - i
					j = i + H[k];
					if ((i < j && j < k) && (H[j] == k - j) && (s.find(j) == s.end())) ++ans, s.insert(j);
				}
			}
		}
		return ans;
	}
	bool ok = true;
	for (int i = 1; i < N; i++) if (H[i] < H[i - 1]) ok = false;
	if (ok) {
		long long ans = 0;
		std::set<int> s;
		for (int k = 0; k < N; k++) {
			int i = k - H[k];
			if (i < 0) continue;
			s.clear();
			// H[i] = k - j || H[i] = j - i
			int j;
			// H[i] = k - j
			j = k - H[i];
			if (i < j && j < k && H[j] == j - i && s.find(j) == s.end()) ++ans, s.insert(j);
			// H[i] = j - i
			j = i + H[i];
			if (i < j && j < k && H[j] == k - j && s.find(j) == s.end()) ++ans, s.insert(j);
		}
		return ans;
	}
	return 0LL;
}

std::vector<int> construct_range(int M, int K) {
	std::vector<int> H(M);
	for (int i = 0; i < M; i++) {
		H[i] = 1;
		if (i % 4 == 2) H[i] = 2;
		if (i % 4 == 3) H[i] = 3;
	}
	return H;
}

• Subtask 0: 0 / 0
• Subtask 1: 8 / 8
• Subtask 2: 6 / 6
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 0 / 16
• Subtask 6: 0 / 19
• Subtask 7: 3.6667 / 5
• Subtask 8: 1.555 / 5
• Subtask 9: 0.6247 / 5
• Subtask 10: 0.2678 / 5
• Subtask 11: 0.3125 / 5
• Subtask 12: 0.1042 / 5