Submission #1107127

#	Time	Username	Problem	Language	Result	Execution time	Memory
1107127		xnqs	Triple Jump (JOI19_jumps)	C++17	0 / 100	24 ms	37328 KiB

jumps

// TODO implement optimally

#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <utility>
#include <algorithm>
#include <cmath>

int x, q;
int arr[500005];
int sp_tb[19][500005];

void build_sparse_table() {
	for (int l = 1; l < 19; l++) {
		for (int i = 1; i+(1<<l)-1 <= x; i++) {
			sp_tb[l][i] = std::max(sp_tb[l-1][i],sp_tb[l-1][i+(1<<(l-1))]);
		}
	}
}

int max_query(int l, int r) {
	int lvl = 31-__builtin_clz(r-l+1);
	return std::max(sp_tb[lvl][l], sp_tb[lvl][r-(1<<lvl)+1]);
}

struct PQComp {
	bool operator() (int a, int b) {
		return arr[a] < arr[b];
	}
};

// take the 2 maxes, let their positions be 1 and 2
// therefore we have the following cases
//
// 1: ---1##--2
// 2: --###1--2
// 3: -1-2-####
int query(int l, int r) {
	if (r-l+1<=50) {
		int ret = 0;
		for (int i = l; i <= r; i++) {
			for (int j = i+1; j <= r; j++) {
				if (j+(j-i)>r) {
					break;
				}

				ret = std::max(ret, arr[i]+arr[j]+max_query(j+(j-i),r));
			}
		}
		return ret;
	}

	std::priority_queue<int, std::vector<int>, PQComp> pq;
	for (int i = l; i <= r; i++) {
		pq.emplace(i);
	}

	std::vector<int> pos;
	while (!pq.empty()&&pos.size()<10) {
		int k = pq.top();
		pq.pop();
		pos.emplace_back(k);
	}

	int ret = 0;
	for (auto m1 : pos) {
		for (auto m2 : pos) {
			if (m1==m2) {
				continue;
			}

			if (m1>m2) std::swap(m1,m2);

			int le, ri;

			// 1
			if (m1+1<m2) {
				le = m1+1;
				ri = (m1+m2)/2;
				ret = std::max(ret,arr[m1]+arr[m2]+max_query(le,ri));
			}

			// 2
			if (m1-1>=l) {
				le = std::max(l,m1-(m2-m1));
				ri = m1-1;
				ret = std::max(ret,arr[m1]+arr[m2]+max_query(le,ri));
			}
			
			// 3
			if (m2+(m2-m1)<=ri) {
				le = m2+(m2-m1);
				ri = r;
				ret = std::max(ret,arr[m1]+arr[m2]+max_query(le,ri));
			}
		}
	}

	return ret;
}

int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(NULL);
	std::cout.tie(NULL);

	std::cin >> x;
	for (int i = 1; i <= x; i++) {
		std::cin >> arr[i];
		sp_tb[0][i] = arr[i];
	}

	build_sparse_table();
	std::cin >> q;
	while (q--) {
		int l, r;
		std::cin >> l >> r;
		std::cout << query(l,r) << "\n";
	}
}

Compilation message (stderr)

jumps.cpp: In function 'int query(int, int)':
jumps.cpp:93:4: warning: 'ri' may be used uninitialized in this function [-Wmaybe-uninitialized]
   93 |    if (m2+(m2-m1)<=ri) {
      |    ^~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 14
• Subtask 3: 0 / 27
• Subtask 4: 0 / 54