Submission #884695

#	Time	Username	Problem	Language	Result	Execution time	Memory
884695		cocohearts	Hacker (BOI15_hac)	C++17	100 / 100	44 ms	5688 KiB

hac

#include "bits/stdc++.h"
using namespace std;

using ll = long long;
using ld = long double;
using db = double;
using str = string;

using pi = pair<int, int>;
using pl = pair<ll, ll>;
using pd = pair<db, db>;

using vi = vector<int>;
using vvi = vector<vi>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<db>;
using vs = vector<str>;
using vpi = vector<pi>;
using vpl = vector<pl>;
using vpd = vector<pd>;

#define mp make_pair
#define f first
#define s second

// const int MOD = 1e9 + 7;
// const int MX = 2e5 + 5;
const int INF = 1e9;
// const ll INF = 1e18;  // not too close to LLONG_MAX
// const ld PI = acos((ld)-1);
// const int dx[4] = {1, 0, -1, 0},
//           dy[4] = {0, 1, 0, -1};  // for every grid problem!!

#define sz(x) int(x.size())
#define bg(x) begin(x)
#define all(x) bg(x), end(x)
#define rall(x) x.rbegin(), x.rend()
#define sor(x) sort(all(x))
#define rsz resize
#define ins insert
#define ft front()
#define bk back()
#define pb push_back
#define eb emplace_back
#define pf push_front

#define lb lower_bound
#define ub upper_bound

#define endl "\n"

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) FOR(i, 0, a)
#define ROF(i, a, b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i, a) ROF(i, 0, a)
#define trav(a, x) for (auto &a : x)

template <class T> using pqg = priority_queue<T, vector<T>, greater<T>>;

constexpr int pct(int x) { return (int)__builtin_popcount(x); }
constexpr int bits(int x) {
	return x == 0 ? 0 : 31 - (int)__builtin_clz(x);
}
 
template <typename T, typename... U>
void dbgh(const T& t, const U&... u) {
    cerr << t;
    ((cerr << " | " << u), ...);
    cerr << endl;
}
 
void setPrec() { cout << fixed << setprecision(15); }
void unsyncIO() { cin.tie(0)->sync_with_stdio(0); }

void setIn(str s) { freopen(s.c_str(), "r", stdin); }
void setOut(str s) { freopen(s.c_str(), "w", stdout); }
void setIO(str s = "") {
	unsyncIO();
	setPrec();
	cin.exceptions(cin.failbit);

	if (sz(s)) setIn(s + ".in"), setOut(s + ".out");
}

#ifdef LOCAL
	const int L = 100;
	#define dbg(...)                                           \
		cerr << "L" << __LINE__ << " [" << #__VA_ARGS__ << "]" \
			<< ": ";                                           \
		dbgh(__VA_ARGS__)
#else
	const int L = 500000;
	#define dbg(...)
#endif

int nums[L];

void solve() {
	int n; cin >> n;
	F0R(i,n) cin >> nums[i];
	int ct = (n+1)/2;
	int ans = -1*INF;
	deque<int> myQ;
	// ind starts at 0
	int sum = 0;
	FOR(ind,n-ct,n) sum += nums[ind%n];
	FOR(ind,n-ct,n) {
		sum += nums[(ind+ct)%n];
		sum -= nums[ind];
		while (myQ.size()) {
			if (myQ.back()>sum) myQ.pop_back();
			else break;
		}
		myQ.push_back(sum);
	}
	int total = 0;
	F0R(ind,n) total += nums[ind];

	F0R(ind,n) {
		ans = max(ans,myQ.front());
		sum += nums[(ind+ct)%n];
		sum -= nums[ind];
		while (myQ.size()) {
			if (myQ.back()>sum) myQ.pop_back();
			else break;
		}
		myQ.push_back(sum);
		int removed = total-sum;
		if (n%2) {
			removed += nums[(ind+ct)%n];
		}
		if (myQ.front()==removed) myQ.pop_front();
	}
	cout << ans;
}

int main() {
	#ifdef LOCAL // call with -DLOCAL
		freopen("../input.txt", "r", stdin);
		freopen("../myoutput.txt", "w", stdout);
		freopen("../debug.txt", "w", stderr);
	#else
		setIO();
	#endif

	solve();
}

Compilation message (stderr)

hac.cpp: In function 'void setIn(str)':
hac.cpp:76:28: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 | void setIn(str s) { freopen(s.c_str(), "r", stdin); }
      |                     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
hac.cpp: In function 'void setOut(str)':
hac.cpp:77:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   77 | void setOut(str s) { freopen(s.c_str(), "w", stdout); }
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 40 / 40