Submission #998182

#	Time	Username	Problem	Language	Result	Execution time	Memory
998182		jcelin	Sparklers (JOI17_sparklers)	C++14	100 / 100	41 ms	8136 KiB

sparklers

#include<bits/stdc++.h>
 
using namespace std;
 
#define X first
#define Y second
#define PB push_back
#define PPB pop_back
#define all(x) (x).begin(), (x).end()
 
typedef vector<int> vi; 
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef long long ll;
typedef vector<ll> vll;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef long double ld;
 
const int MAXN = 1e6 + 7;
const int logo = 20;
const int off = 1 << logo;
const int trsz = off << 1;
const int mod = 1e9 + 7;
const ll inf = 1e18 + 7;
const ll INF = 1e18 + 7;
 
ll x[MAXN], n, k, t;
vll lef, rig;
vpll L, R, nl, nr;
 
bool okej(ll poc, vpll &vec){
	for(auto &y : vec){
		if(poc + y.Y < 0) return 0;
		poc += y.X;
	}
	return poc >= 0;
}


bool moze(ll csu, vpll L, vpll R){
	int li = 0, ri = 0;
	while(1){
		pll c1 = {-inf, -inf}, c2 = {-inf, -inf};
		
		if(li < (int)L.size()) c1 = L[li];
		if(ri < (int)R.size()) c2 = R[ri];
		
		if(c1.X == -inf and c2.X == -inf) return 1;
		
		if(csu + c1.Y >= 0){
			csu += c1.X;
			li++;
			continue;
		}
		
		if(csu + c2.Y >= 0){
			csu += c2.X;
			ri++;
			continue;
		}
		
		return 0;
	}
}

bool check(ll mid){
	lef.clear();
	rig.clear();
	L.clear();
	R.clear();
	nl.clear();
	nr.clear();
	
	ll sum = 0;
	for(int i=k; i<n; i++) rig.PB((ll)2 * mid * t - (ll)(x[i + 1] - (ll)x[i]) / 2), sum += rig.back();
	for(int i=1; i<k; i++) lef.PB((ll)2 * mid * t - (ll)(x[i + 1] - (ll)x[i]) / 2), sum += lef.back();
	reverse(all(lef));
	if(sum < 0) return 0;
	
	ll csu = 0, mi = 0;
	int ls = -1;
	for(int i=0; i<(int)rig.size(); i++){
		csu += rig[i];
		mi = min(mi, csu);
		if(csu >= 0){
			R.PB({csu, mi});
			csu = mi = 0;
			ls = i;
		}
	}
	
	csu = mi = 0;
	for(int i=(int)rig.size() - 1; i>ls; i--){
		csu -= rig[i];
		mi = min(mi, csu);
		if(csu >= 0){
			nr.PB({csu, mi});
			csu = mi = 0;
		}
	}
	
	
	csu = 0, mi = 0;
	ls = -1;
	for(int i=0; i<(int)lef.size(); i++){
		csu += lef[i];
		mi = min(mi, csu);
		if(csu >= 0){
			L.PB({csu, mi});
			csu = mi = 0;
			ls = i;
		}
	}
	
	csu = mi = 0;
	for(int i=(int)lef.size() - 1; i>ls; i--){
		csu -= lef[i];
		mi = min(mi, csu);
		if(csu >= 0){
			nl.PB({csu, mi});
			csu = mi = 0;
		}
	}
	
	return moze(0, L, R) and moze(sum, nl, nr);
}
 
void solve(){
	cin >> n >> k >> t;
	for(int i=1; i<=n; i++) cin >> x[i], x[i] *= 2;
	
	int lo = 0, hi = ((1e9 + 1) / t) + 1, ret = -1;
	while(lo <= hi){
		int mid = (lo + hi) / 2;
		if(check(mid)) hi = mid - 1, ret = mid;
		else lo = mid + 1;
	}
	cout << ret << "\n";
}
 
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int tt = 1;
	//cin >> t;
	while(tt--) solve();
	return 0;
}

/*
-15708 2615 22272 -6638 -35674 -50958 41359 -1318 
-33710 -40703 4522 12061
*/

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 50 / 50