Submission #838296

#	Time	Username	Problem	Language	Result	Execution time	Memory
838296		siewjh	Rainforest Jumps (APIO21_jumps)	C++17	100 / 100	1002 ms	51376 KiB

jumps

#include "jumps.h"
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 200005;
int nums, height[MAXN], lf[MAXN][20], rt[MAXN][20], hi[MAXN][20];

int query(int l, int r, int targ){
	int ans = r;
	if (height[ans] > targ) return -1;
	for (int k = 19; k >= 0; k--)
		if (lf[ans][k] >= l && height[lf[ans][k]] < targ)
			ans = lf[ans][k];
	return ans;
}

void init(int N, vector<int> H) {
	nums = N;
	for (int i = 1; i <= nums; i++) height[i] = H[i - 1];
	height[0] = height[nums + 1] = nums + 1;
	stack<pair<int, int>> s;
	s.push({nums + 1, 0});
	for (int i = 1; i <= nums; i++){
		while (height[i] > s.top().first) s.pop();
		lf[i][0] = s.top().second;
		s.push({height[i], i});
	}
	while (s.size()) s.pop();
	s.push({nums + 1, nums + 1});
	for (int i = nums; i >= 1; i--){
		while (height[i] > s.top().first) s.pop();
		rt[i][0] = s.top().second;
		s.push({height[i], i});
	}
	for (int i = 1; i <= nums; i++) hi[i][0] = (height[lf[i][0]] > height[rt[i][0]] ? lf[i][0] : rt[i][0]);
	for (int k = 1; k < 20; k++)
		for (int i = 1; i <= nums; i++){
			if (lf[i][k - 1] == 0) lf[i][k] = 0;
			else lf[i][k] = lf[lf[i][k - 1]][k - 1];
			if (rt[i][k - 1] == nums + 1) rt[i][k] = nums + 1;
			else rt[i][k] = rt[rt[i][k - 1]][k - 1];
			if (hi[i][k - 1] == 0 || hi[i][k - 1] == nums + 1) hi[i][k] = hi[i][k - 1];
			else hi[i][k] = hi[hi[i][k - 1]][k - 1];
		}
}

int minimum_jumps(int A, int B, int C, int D) {
	A++; B++; C++; D++;
	int maxcd = height[query(C, D, MAXN)], curr = query(A, B, maxcd);
	if (curr == -1) return -1;
	int ans = 0;
	for (int k = 19; k >= 0; k--)
		if (height[hi[curr][k]] != nums + 1 && rt[hi[curr][k]][0] < C){
			curr = hi[curr][k];
			ans += (1 << k);
		}
	if (rt[curr][0] < C && height[hi[curr][0]] != nums + 1 && rt[hi[curr][0]][0] <= D){
		ans++;
		curr = hi[curr][0];
	}
	for (int k = 19; k >= 0; k--)
		if (rt[curr][k] < C){
			curr = rt[curr][k];
			ans += (1 << k);
		}
	if (rt[curr][0] > D) return -1;
	else return ans + 1;
}

• Subtask 1: 4 / 4
• Subtask 2: 8 / 8
• Subtask 3: 13 / 13
• Subtask 4: 12 / 12
• Subtask 5: 23 / 23
• Subtask 6: 21 / 21
• Subtask 7: 19 / 19