Submission #393315

#	Time	Username	Problem	Language	Result	Execution time	Memory
393315		JimmyZJX	Mountains (IOI17_mountains)	C++14	100 / 100	45 ms	31724 KiB

mountains

#include <iostream>
#include <fstream>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cassert>
#include <tuple>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <unordered_set>
#include <unordered_map>
#include <numeric>

using namespace std;

typedef long long LL;
typedef vector<int> Vi;
typedef vector<LL> VL;
typedef vector<bool> Vb;
typedef vector<vector<int>> Vii;

#define forR(i, n) for (int i = 0; i < (n); i++)

template <typename T>
vector<size_t> sort_indexes(vector<T> v) {
	vector<size_t> idx(v.size());
	iota(idx.begin(), idx.end(), 0);

	stable_sort(idx.begin(), idx.end(),
		[&v](size_t i1, size_t i2) {return v[i1] < v[i2]; });

	return idx;
}

int see[2003][2003];
int dp[2003][2003];

struct Frac { // a / b
	int a, b;
};

bool ge(Frac x, Frac y) {
	return (LL)x.a * y.b >= (LL)y.a * x.b;
}

int maximum_deevs(Vi y) {
	int n = y.size();
	memset(see, 0, sizeof(see));

	Vi cnt(n);

	forR(i, n) {
		Frac view{ INT_MIN, 1 };
		for (int j = i - 1; j >= 0; j--) {
			Frac vj{ y[j] - y[i], i - j };
			if (ge(vj, view)) {
				view = vj;
				see[i][j] = 1;
				cnt[i]++;
			}
		}
		view = { INT_MIN, 1 };
		for (int j = i + 1; j < n; j++) {
			Frac vj{ y[j] - y[i], j - i };
			if (ge(vj, view)) {
				view = vj;
				see[i][j] = 1;
				cnt[i]++;
			}
		}
	}

	memset(dp, 0, sizeof(dp));
	// dp[i][j]   [i, j)
	forR(i, n) dp[i][i] = 0;

	for (int j = 1; j <= n; j++) {
		dp[j - 1][j] = 1;
		// choose (j-1)
		int last = j - 1;
		int sum = 1;
		for (int k = j - 2; k >= 0; k--) {
			if (see[j - 1][k]) {
				sum += dp[k + 1][last];
				last = k;
			}
			dp[k][j] = max(dp[k][j - 1], dp[k][last] + sum);
		}
	}


	return dp[0][n];
}


#ifdef TEST_LOCAL
int main() {
	auto r = maximum_deevs(Vi{ 0,1,1000000,1500001,1499997,1499992,1499986,1499979,1499971,1499962,1499952,1499941,1499929,1499916,1499902,1499887,1499871,1499854,1000000000 });

	return 0;
}
#endif

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 30 / 30
• Subtask 4: 30 / 30