Submission #1106602

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
1106602	2024-10-30T17:32:12 Z	xnqs	Watching (JOI13_watching)	C++17	50 / 100	190 ms	1532 KB

watching

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

int x, p, q;
std::vector<int> arr;
char dp[101][101][101];

char sol(int pos, int a, int b, int cap) {
	if (a>p||b>q) {
		return 0;
	}
	if (pos==x) {
		return 1;
	}
	if (dp[pos][a][b]!=-1) {
		return dp[pos][a][b];
	}
 
	char ret = 0;
	for (int i = pos; i < x; i++) {
		if (arr[i]-arr[pos]+1 <= cap) {
			ret |= sol(i+1,a+1,b,cap);
		}
		if (arr[i]-arr[pos]+1 <= 2*cap) {
			ret |= sol(i+1,a,b+1,cap);
		}
	}
	return dp[pos][a][b] = ret;
}

bool can_solve(int cap, bool debug = 0) {
	if (x<=100) {
		memset(dp,-1,sizeof(dp));
		return sol(0,0,0,cap);
	}
	else {
		std::vector<int> tmp = arr;
		if (debug) {
			for (const auto& i : tmp) {
				std::cout << i << " ";
			}
			std::cout << "\n";
		}
		
		// first use the large cameras
		for (int iterations = 0; iterations < q && !tmp.empty(); iterations++) {
			int w = 2*cap;
			int max = -1, max_l = -1, max_r = -1;
			for (int l = 0, r = 0; r < tmp.size(); r++) {
				while (tmp[r]-tmp[l]+1 > w) {
					++l;
				}
	 
				if (r-l+1>max) {
					max = r-l+1;
					max_l = l;
					max_r = r;
				}
			}
	 
			tmp.erase(tmp.begin()+max_l,tmp.begin()+max_r+1);
			if (debug) {
				std::cout << max_l << " " << max_r << "\n";
				for (const auto& i : tmp) {
					std::cout << i << " ";
				}
				std::cout << "\n";
			}
		}
	 
		// then the small cameras
		for (int iterations = 0; iterations < p && !tmp.empty(); iterations++) {
			int w = cap;
			int max = -1, max_l = -1, max_r = -1;
			for (int l = 0, r = 0; r < tmp.size(); r++) {
				while (tmp[r]-tmp[l]+1 > w) {
					++l;
				}
	 
				if (r-l+1>max) {
					max = r-l+1;
					max_l = l;
					max_r = r;
				}
			}
	 
			tmp.erase(tmp.begin()+max_l,tmp.begin()+max_r+1);
			if (debug) {
				std::cout << max_l << " " << max_r << "\n";
				for (const auto& i : tmp) {
					std::cout << i << " ";
				}
				std::cout << "\n";
			}
		}
		
		return tmp.empty();
	}
}
 
int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(NULL);
	std::cout.tie(NULL);
 
	std::cin >> x >> p >> q;
 
	// we only need at most x cameras in total, out of which we'll greedily take as many big cameras as possible
	if (p+q>x) {
		q = std::min(q, x);
		p = x-q;
	}
 
	for (int i = 0, tmp; i < x; i++) {
		std::cin >> tmp;
		arr.emplace_back(tmp);
	}
 
	std::sort(arr.begin(),arr.end());
	const auto bs = [&]() {
		int ret = 1000000001;
		int l = 1, r = 1000000000;
		while (l<=r) {
			int m = (l+r)>>1;
			if (can_solve(m)) {
				ret = m;
				r = m-1;
			}
			else {
				l = m+1;
			}
		}
		return ret;
	};
 
	std::cout << bs() << "\n";
	//can_solve(bs(),1);
}

Compilation message

watching.cpp: In function 'bool can_solve(int, bool)':
watching.cpp:54:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   54 |    for (int l = 0, r = 0; r < tmp.size(); r++) {
      |                           ~~^~~~~~~~~~~~
watching.cpp:80:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   80 |    for (int l = 0, r = 0; r < tmp.size(); r++) {
      |                           ~~^~~~~~~~~~~~

Subtask #1

50.0 / 50.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	4 ms	1360 KB	Output is correct
2	Correct	2 ms	1360 KB	Output is correct
3	Correct	2 ms	1360 KB	Output is correct
4	Correct	52 ms	1360 KB	Output is correct
5	Correct	7 ms	1360 KB	Output is correct
6	Correct	7 ms	1360 KB	Output is correct
7	Correct	9 ms	1532 KB	Output is correct
8	Correct	16 ms	1360 KB	Output is correct
9	Correct	18 ms	1360 KB	Output is correct
10	Correct	75 ms	1360 KB	Output is correct
11	Correct	85 ms	1360 KB	Output is correct
12	Correct	190 ms	1360 KB	Output is correct
13	Correct	21 ms	1528 KB	Output is correct
14	Correct	23 ms	1360 KB	Output is correct
15	Correct	20 ms	1468 KB	Output is correct

Subtask #2

0 / 50.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	1 ms	336 KB	Output isn't correct
2	Halted	0 ms	0 KB	-