Submission #1170514

#	Time	Username	Problem	Language	Result	Execution time	Memory
1170514		baldwin_huang	Rainforest Jumps (APIO21_jumps)	C++20	0 / 100	23 ms	40408 KiB

jumps

#include <bits/stdc++.h>

using namespace std;

int n;
vector<int> h;
const int INF = 1e9;

struct node {
	int left = -1;
	int right = -1;
};

vector<node> nodes;
vector<int> height_to_index(262144 + 10);
vector< vector<int> > binary_lifting(262144 + 10, vector<int>(30, -1)); // It tells you the height of the 2^jth ancestor of i.

void init(int N, vector<int> H) {
	n = N;
	h = H;
	nodes = vector<node>(n); // It's a graph, has the index to the children.

	for (int i = 1; i < n; i++) {
		int target = i - 1;
		while (H[target] <= H[i]) {
			if (target == -1) {
				break;
			}
			target = nodes[target].left;
		}
		nodes[i].left = target;
	}

	for (int i = n - 2; i >= 0; i--) {
		int target = i + 1;
		while (H[target] <= H[i]) {
			if (target == -1) {
				break;
			}
			target = nodes[target].right;
		}
		nodes[i].right = target;
	}

	// Create the binary_lift

	// Create the base ancestors;
	for (int i = 0; i < n; i++) {
		binary_lifting[i][0] = max(nodes[i].left, nodes[i].right);
	}

	for (int i = 1; i < 30; i++) {
		for (int j = 0; j < n; j++) {
			if (binary_lifting[j][i - 1] == -1) {
				binary_lifting[j][i] = -1;
			}
			else {
				binary_lifting[j][i] = binary_lifting[binary_lifting[j][i - 1]][i - 1];
			}
		}
	}

	for (int i = 0; i < n; i++) {
		height_to_index[h[i]]= i;
	}

	// cout << "Ancestor: " << binary_lifting[1][1] << '\n';

	return;
}

// Return the index of the closest approximate of how many to jump.
int final_index;
int closest(int source, int height) {
	int high = 29;
	int low = 0;
	int ans = -1;
	// Find the greatest ancestor that doesn't exceed or equal the height
	// In theory, if the source is too large, then it should just return 0.
	while (low <= high) {
		int mid = (low + high) / 2;

		if (binary_lifting[source][mid] != -1 && binary_lifting[source][mid] < height) {
			ans = mid;
			low = mid + 1;
		}
		else {
			high = mid - 1;
		}
	}

	cout << "ANS: " << ans << '\n';
	if (ans == -1) {
		// My parent is already optimal.
		return -1;
	}
	int child_ans = closest(binary_lifting[source][ans], height - (1<<ans));
	if (child_ans == -1) {
		// My children thinks I am the optimal one.
		final_index = height_to_index[binary_lifting[source][ans]];
		return 1<<ans; // The amount I jumped.
	}
	else {
		return (1<<ans) + child_ans;
	}
}

int minimum_jumps(int A, int B, int C, int D) {

	if (A != B || C != D) {
		return -1;
	}

	// Find the greatest height only using the greater neighbour that does not exceed C.
	int closest_amount = closest(A, h[C]);
	cout << final_index << '\n';

	if ((nodes[final_index].left + closest_amount + h[A]) == h[C] || (nodes[final_index].right + closest_amount + h[A]) == h[C]) {
		return closest_amount + 1;
	}
	else {
		return -1;
	}
	
}

• Subtask 1: 0 / 4
• Subtask 2: 0 / 8
• Subtask 3: 0 / 13
• Subtask 4: 0 / 12
• Subtask 5: 0 / 23
• Subtask 6: 0 / 21
• Subtask 7: 0 / 19