Submission #558104

#	Time	Username	Problem	Language	Result	Execution time	Memory
558104		aryan12	The Big Prize (IOI17_prize)	C++17	20 / 100	40 ms	2048 KiB

prize

#include "prize.h"
#include <bits/stdc++.h>
using namespace std;

const int MAXN = 450;
vector<pair<int, int> > values(200001, {-1, -1});
bool ischecked[200001];
int N, best_sum = 0;

bool cmp(array<int, 3> a, array<int, 3> b)
{
	return ((a[0] + a[1]) > (b[0] + b[1]));
}


int DivideAndConquer(int l, int r, int parent_value, int parent_left, int parent_right) // index of diamond (-1 if not found)
{
	// cout << "l = " << l << ", r = " << r << ", parent_value = " << parent_value << ", parent_left = " << parent_left << ", parent_right = " << parent_right << endl;
	if(l > r)
	{
		return -1;
	}
	int mid = (l + r) >> 1;
	vector<int> current_reply(2);
	int cur_l = mid, cur_r = mid, cnt = 0;
	while(cnt <= MAXN)
	{
		cnt++;
		if(cnt % 2 == 1)
		{
			if(cur_l >= l && !ischecked[cur_l])
			{
				if(values[cur_l].first == -1)
				{
					current_reply = ask(cur_l);
					values[cur_l] = {current_reply[0], current_reply[1]};
				}
				if(values[cur_l].first + values[cur_l].second == best_sum)
				{
					mid = cur_l;
					break;
				}
				cur_l--;
			}
		}
		else
		{
			if(cur_r < r && !ischecked[cur_r])
			{
				if(values[cur_r].first == -1)
				{
					current_reply = ask(cur_r);
					values[cur_r] = {current_reply[0], current_reply[1]};
				}
				if(values[cur_r].first + values[cur_r].second == best_sum)
				{
					mid = cur_r;
					break;
				}
				cur_r++;
			}
		}
	}
	// cout << "mid = " << mid << endl;
	// cout << "l = " << l << ", r = " << r << ", mid = " << mid << "\n";
	// values[mid] = {current_reply[0], current_reply[1]};
	current_reply = {values[mid].first, values[mid].second};
	ischecked[mid] = true;
	if(current_reply[0] + current_reply[1] == 0)
	{
		return mid;
	}
	if(parent_left + parent_right != current_reply[0] + current_reply[1])
	{
		// higher to lower or vice versa, don't do anything based on parent
		if(current_reply[0] != 0)
		{
			int value = DivideAndConquer(l, mid - 1, mid, current_reply[0], current_reply[1]);
			if(value != -1) // value found
			{
				return value;
			}
		}
		if(current_reply[1] != 0)
		{
			int value = DivideAndConquer(mid + 1, r, mid, current_reply[0], current_reply[1]);
			if(value != -1) // value found
			{
				return value;
			}
		}
		return -1; // value not found in both children
	}

	// equal value of parent and current
	// if current is the left child of parent do:
	//     parent_left == current_left: No need to check right child
	// else if current is the right child of parent do:
	//     parent_right == current_left: No ned to check right child

	if(parent_value == r + 1) // current is the left child of parent
	{
		if(current_reply[0] != 0)
		{
			int value = DivideAndConquer(l, mid - 1, mid, current_reply[0], current_reply[1]);
			if(value != -1) // value found
			{
				return value;
			}
		}
		if(current_reply[1] != 0 && current_reply[0] != parent_left)
		{
			int value = DivideAndConquer(mid + 1, r, mid, current_reply[0], current_reply[1]);
			if(value != -1) // value found
			{
				return value;
			}
		}
		return -1;
	}
	else
	{
		if(current_reply[0] != 0)
		{
			int value = DivideAndConquer(l, mid - 1, mid, current_reply[0], current_reply[1]);
			if(value != -1) // value found
			{
				return value;
			}
		}
		if(current_reply[1] != 0 && current_reply[0] != parent_right)
		{
			int value = DivideAndConquer(mid + 1, r, mid, current_reply[0], current_reply[1]);
			if(value != -1) // value found
			{
				return value;
			}
		}
		return -1;
	}
}

int find_best(int n)
{
	int mid = n / 2 - 1;
	N = n;
	for(int i = mid - MAXN / 2; i <= mid + MAXN / 2; i++)
	{
		// cout << "i = " << i << "\n";
		if(i < 0 || i > N)
		{
			continue;
		}
		vector<int> reply = ask(i);
		values[i] = {reply[0], reply[1]};
		best_sum = max(best_sum, reply[0] + reply[1]);
	}
	return DivideAndConquer(0, n - 1, n, 0, 0);
}

• Subtask 1: 20 / 20
• Subtask 2: 0 / 80