Submission #377032

#	Time	Username	Problem	Language	Result	Execution time	Memory
377032		SavicS	Watching (JOI13_watching)	C++14	100 / 100	202 ms	16236 KiB

watching

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>

#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ff(i,a,b) for(int i=a;i<=b;i++)
#define fb(i,b,a) for(int i=b;i>=a;i--)

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,int> pii;
const int maxn = 2005;
const int inf = 1e9 + 5;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k)  print the k-th smallest number in os(0-based)

int n, p, q;
ll niz[maxn];

// p, q <= 1e5 i n <= 2000
// naive: n^2 * p * q
 
// za a malih kamera, koliko mi treba velikih da slikam prvih i proslova - dp[a][i]
// dp[a][i] <= q return 1, else return 0

int dp[maxn][maxn];
bool check(ll x){
	int jp = 1;
	int jq = 1;
	memset(dp, 0, sizeof(dp));
	ff(i,1,n){

		while(niz[i] - niz[jp] >= x)jp += 1;
		while(niz[i] - niz[jq] >= 2 * x)jq += 1;
		
		ff(j,0,p){
			if(j != 0){
				// ili uradim sa malom kamerom [jp, i]
				// ili uradim sa velikom kamerom [jq, i], ali dodam jedan
				dp[i][j] = min(dp[jp - 1][j - 1], dp[jq - 1][j] + 1);
			}
			else dp[i][j] = dp[jq - 1][j] + 1;
		}
	}	
	int mn = inf;
	ff(j,0,p)mn = min(mn, dp[n][j]);
	return mn <= q;
}

int main()
{
   	ios::sync_with_stdio(false);
   	cout.tie(nullptr);
  	cin.tie(nullptr);
	cin >> n >> p >> q;
	ff(i,1,n)cin >> niz[i];
	
	if(p + q >= n)return cout << 1, 0;
	
	sort(niz + 1, niz + n + 1);
	
	int l = 1, r = inf, ans = inf;
	while(l <= r){
		int mid = (l + r) / 2;
		if(check(mid)){
			ans = mid;
			r = mid - 1;
		}
		else l = mid + 1;
	}
	cout << ans << endl;
   	return 0;
}
/**

3 1 1
2
11
17


// probati bojenje sahovski ili slicno

**/

• Subtask 1: 50 / 50
• Subtask 2: 50 / 50