oj.uz

Submission #708685

# Submission time Handle Problem Language Result Execution time Memory
708685 2023-03-12T07:31:53 Z Green55 Mountains (IOI17_mountains) C++17
0 / 100
 1 ms 340 KB 
#include "mountains.h"
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define xx first
#define yy second
#define all(v) (v).begin(), (v).end()

// * dp[l][r] : r을 반드시 포함하여 l~r에서 지을 수 있는 최대 개수
// k[] = r에서 보이는 점들의 인덱스들을 순서대로 쓴 배열.
// -> dp[l][r]은 k를 기준으로 partition을 나눠서, 각 최적을 합한 것과 같다.
// k[i] = k[]에서 l의 lower bound.
// opt(x ~ y) = 구간 [i~j]에서 max dp값.
// dp[l][r] = opt(l ~ k[i]-1) + opt(k[i]+1, k[i+1]-1) + ...+ opt(k[-2]+1, k[-1]-1) + 1

int n, dp[2020][2020], opt[2020][2020];
ll h[2020];

int get_opt(int l, int r) {
	auto &ret = opt[l][r];
	if(ret != -1) return ret;
	ret = dp[l][r];
	if(l != r)
		ret = max({ret, get_opt(l+1, r), get_opt(l, r-1)});
	return ret;
}

bool canSee(int l, int mid, int r) {
	return (mid - l)*(h[r] - h[l]) - (r - l)*(h[mid] - h[l]) >= 0;
}

int maximum_deevs(vector<int> _y){
	n = _y.size();
	for(int i=1; i<=n; ++i) h[i] = _y[i-1];

	for(int i=0; i<=n+1; ++i)
		for(int j=0; j<=n+1; ++j)
			dp[i][j] = opt[i][j] = -1;

	dp[1][1] = 1;
	for(int r=2; r<=n; ++r) {
		vector<int> ks = {r-1};
		for(int l=r-2; l>=2; --l)
			if(canSee(l, ks.back(), r))
				ks.push_back(l);
		if(ks.back() != 1) ks.push_back(1);
		
		dp[r][r] = dp[r-1][r] = 1;
		int opt_sum = 1;
		for(int ki=1; ki<ks.size(); ++ki) {
			int k2 = ks[ki-1], k1 = ks[ki];
			for(int l=k1+1; l<k2; ++l)
				dp[l][r] = opt_sum + get_opt(l, k2-1);
			if(k1+1 <= k2-1)
				opt_sum += get_opt(k1+1, k2-1);
			
			dp[k1][r] = opt_sum;
		}
	}

	return get_opt(1, n);
}

Compilation message

mountains.cpp: In function 'int maximum_deevs(std::vector<int>)':
mountains.cpp:52:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   52 |   for(int ki=1; ki<ks.size(); ++ki) {
      |                 ~~^~~~~~~~~~

Subtask #1
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 340 KB Output is correct
2 Correct 1 ms 316 KB Output is correct
3 Incorrect 0 ms 340 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #2
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 340 KB Output is correct
2 Correct 1 ms 316 KB Output is correct
3 Incorrect 0 ms 340 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #3
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 340 KB Output is correct
2 Correct 1 ms 316 KB Output is correct
3 Incorrect 0 ms 340 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #4
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 340 KB Output is correct
2 Correct 1 ms 316 KB Output is correct
3 Incorrect 0 ms 340 KB Output isn't correct
4 Halted 0 ms 0 KB -