Submission #699701

#	Time	Username	Problem	Language	Result	Execution time	Memory
699701		Zflop	Hacker (BOI15_hac)	C++14	100 / 100	311 ms	18392 KiB

hac

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

/*
ID: 10002181
LANG: C++
TASK: lamps
*/

using str = string; // yay python!
using ld = long double; // or double, if TL is tight
using ll = long long;
using int64 = ll;
using db = double;
using ull = unsigned long long;

#define ch() getchar()
#define pc(x) putchar(x)
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>;
tcT, size_t SZ> using AR = array<T,SZ>;
using vi = V<int>;
using vb = V<bool>;
using vpi = V<pair<int,int>>;
using vvi = V<vi>;
using vl = V<ll>;
using vd = V<ld>;
using vstr = V<str>;

#define all(x) begin(x), end(x)
#define sor(x) sort(all(x))
#define rev(x) reverse(all(x))
#define sz(x) (int)(x).size()
#define rall(x) x.rbegin(), x.rend()
#define AR array

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

// pairs
#define mp make_pair
#define pi pair <int, int>
#define f first
#define s second

// vectors
#define lb lower_bound
#define ub upper_bound
#define SUM(v) accumulate(all(v), 0LL)
#define MN(v) *min_element(all(v))
#define MX(v) *max_element(all(v))
#define UNIQUE(a) (a).erase(unique((a).begin(),(a).end()),(a).end())
#define eb emplace_back
#define ft front()
#define bk back()
#define ins insert
#define pf push_front
#define pb push_back
#define emt empty()
#define rsz resize

#define pob pop_back()
#define pof pop_front()

#define swp(a,b) a^=b^=a^=b

#define ts to_string

#define setIO()  ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)

const ll MOD = 1e9+7;
const ll MAX = 100000000000;
const ll INF = 1e18; // not too close to LLONG_MAX
const ld PI = acos((ld)-1);

#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1}; // for every grid problem!!

tcT> bool ckmin(T& a, const T& b) {
	return b < a ? a = b, 1 : 0; } // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
	return a < b ? a = b, 1 : 0; }

tcTU> T fstTrue(T lo, T hi, U f) {
	hi ++; assert(lo <= hi); // assuming f is increasing
	while (lo < hi) { // find first index such that f is true
		T mid = lo+(hi-lo)/2;
		f(mid) ? hi = mid : lo = mid+1;
	}
	return lo;
}
tcTU> T lstTrue(T lo, T hi, U f) {
	lo --; assert(lo <= hi); // assuming f is decreasing
	while (lo < hi) { // find first index such that f is true
		T mid = lo+(hi-lo+1)/2;
		f(mid) ? lo = mid : hi = mid-1;
	}
	return lo;
}

//INPUT
#define tcTUU tcT, class ...U
tcT> void re(complex<T>& c);
tcTU> void re(pair<T,U>& p);
tcT> void re(V<T>& v);
tcT, size_t SZ> void re(AR<T,SZ>& a);

tcT> void re(T& x) { cin >> x; }
void re(db& d) { str t; re(t); d = stod(t); }
void re(ld& d) { str t; re(t); d = stold(t); }
tcTUU> void re(T& t, U&... u) { re(t); re(u...); }

tcT> void re(complex<T>& c) { T a,b; re(a,b); c = {a,b}; }
tcTU> void re(pair<T,U>& p) { re(p.f,p.s); }
tcT> void re(V<T>& x) { trav(a,x) re(a); }
tcT> void rv(int n, V<T>& x) { x.rsz(n); re(x); }

//OUTPUT
namespace output {
	tcT> void PS(V<T>& x) { FOR(i,sz(x)) cout << x[i] << " \n"[i + 1 == sz(x)];}
	tcT> void PS(bool ok) { if(ok) cout << "YES\n"; else cout << "NO\n"; }
    template<class T1, class T2> void pr(const pair<T1,T2>& x);
    tcT, size_t SZ> void pr(const array<T,SZ>& x);
    tcT> void pr(const vector<T>& x);
    tcT> void pr(const set<T>& x);
    template<class T1, class T2> void pr(const map<T1,T2>& x);

    tcT> void pr(const T& x) { cout << x; }
    template<class Arg, class... Args> void pr(const Arg& first, const Args&... rest) {
        pr(first); pr(rest...);
    }

    template<class T1, class T2> void pr(const pair<T1,T2>& x) {
        pr("{",x.f,", ",x.s,"}");
    }
    tcT> void prContain(const T& x) {
        pr("{");
        bool fst = 1; trav(a,x) pr(!fst?", ":"",a), fst = 0;
        pr("}");
    }
    tcT, size_t SZ> void pr(const array<T,SZ>& x) { prContain(x); }
    tcT> void pr(const vector<T>& x) { prContain(x); }
    tcT> void pr(const set<T>& x) { prContain(x); }
    template<class T1, class T2> void pr(const map<T1,T2>& x) { prContain(x); }

    void ps() { pr("\n"); } // print w/ spaces
    template<class Arg> void ps(const Arg& first) { pr(first,"\n"); }
    template<class Arg, class... Args> void ps(const Arg& first, const Args&... rest) {
        pr(first," "); ps(rest...);
    }
}

using namespace output;

template <int MOD_> struct modnum {
	static constexpr int MOD = MOD_;
	static_assert(MOD_ > 0, "MOD must be positive");
 
private:
	using ll = long long;
 
	int v;
 
	static int minv(int a, int m) {
		a %= m;
		assert(a);
		return a == 1 ? 1 : int(m - ll(minv(m, a)) * ll(m) / a);
	}
 
public:
 
	modnum() : v(0) {}
	modnum(ll v_) : v(int(v_ % MOD)) { if (v < 0) v += MOD; }
	explicit operator int() const { return v; }
	friend std::ostream& operator << (std::ostream& out, const modnum& n) { return out << int(n); }
	friend std::istream& operator >> (std::istream& in, modnum& n) { ll v_; in >> v_; n = modnum(v_); return in; }
 
	friend bool operator == (const modnum& a, const modnum& b) { return a.v == b.v; }
	friend bool operator != (const modnum& a, const modnum& b) { return a.v != b.v; }
 
	modnum inv() const {
		modnum res;
		res.v = minv(v, MOD);
		return res;
	}
	friend modnum inv(const modnum& m) { return m.inv(); }
	modnum neg() const {
		modnum res;
		res.v = v ? MOD-v : 0;
		return res;
	}
	friend modnum neg(const modnum& m) { return m.neg(); }
 
	modnum operator- () const {
		return neg();
	}
	modnum operator+ () const {
		return modnum(*this);
	}
 
	modnum& operator ++ () {
		v ++;
		if (v == MOD) v = 0;
		return *this;
	}
	modnum& operator -- () {
		if (v == 0) v = MOD;
		v --;
		return *this;
	}
	modnum& operator += (const modnum& o) {
		v += o.v;
		if (v >= MOD) v -= MOD;
		return *this;
	}
	modnum& operator -= (const modnum& o) {
		v -= o.v;
		if (v < 0) v += MOD;
		return *this;
	}
	modnum& operator *= (const modnum& o) {
		v = int(ll(v) * ll(o.v) % MOD);
		return *this;
	}
	modnum& operator /= (const modnum& o) {
		return *this *= o.inv();
	}
 
	friend modnum operator ++ (modnum& a, int) { modnum r = a; ++a; return r; }
	friend modnum operator -- (modnum& a, int) { modnum r = a; --a; return r; }
	friend modnum operator + (const modnum& a, const modnum& b) { return modnum(a) += b; }
	friend modnum operator - (const modnum& a, const modnum& b) { return modnum(a) -= b; }
	friend modnum operator * (const modnum& a, const modnum& b) { return modnum(a) *= b; }
	friend modnum operator / (const modnum& a, const modnum& b) { return modnum(a) /= b; }
};

void setF(string fileName = "") {
	ios_base::sync_with_stdio(0); cin.tie(0);
	if((int)fileName.size()) {
		freopen((fileName+".in").c_str(), "r", stdin);
		freopen((fileName+".out").c_str(), "w", stdout);
	}
}

vi SIEVE(int N){ // sieve in O(N)
	vi pr;
	vb b(N);
	vi g(N);
	F0R(i,2,N){
		if(!b[i]){
			pr.pb(i);
			for (int j = i + i; j < N; j += i) b[j] = true;
			}
		}
	return pr;
	}

struct DSU {
	vector<int> e;
	DSU(int N) { e = vector<int>(N, -1); }

	int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); }

	bool same_set(int a, int b) { return get(a) == get(b); }

	int size(int x) { return -e[get(x)]; }

	bool unite(int x, int y) {  // union by size
		x = get(x), y = get(y);
		if (x == y) return false;
		if (e[x] > e[y]) swap(x, y);
		e[x] += e[y]; e[y] = x;
		return true;
	}
};

struct edge{
	int a;
	int b;
	int w;
	};

ll POW(ll x, ll y,ll mod = INF){
    ll res = 1LL;
    x %= mod;
    while(y){
        if (y & 1LL)
            res *= x;
        res %= mod;
        x = (x*x) % mod;
        y >>= 1LL;
    }
    return res;
}

ll gauss(ll n) { return n * (n + 1ll) / 2; }

ll fact(ll x) { if(x) return x * fact(x - 1ll); return 1; }

vl fc;
void F(int N,ll MOD){
	fc.rsz(N + 1);
	fc[0] = 1;
	FORn(i,N) fc[i] = fc[i - 1] * i * 1ll % MOD;
	}
	
vl inv;
void I(int N,ll MOD){
	inv.rsz(N + 1);
	inv[N] = POW(fc[N],MOD - 2,MOD);
	for (int i = N; i ;--i) inv[i - 1] = inv[i] * 1ll * i % MOD;
	}

ll Cr(ll N,ll K,ll mod){
	if(K < 0) return 0;
	if(K > N) return 0;
	return fc[N] * 1ll * inv[K] % mod * inv[N - K] % mod;
	}

/*
 scanf("%lld", &testInteger);
 printf("%lld", testInteger);

 ____ ____ ____ ____ ____  ____
||f |||l |||o |||p |||p ||||y ||
||__|||__|||__|||__|||__||||__||
|/__\|/__\|/__\|/__\|/__\||/__\|

**/
void solve() {
	int N; cin >> N;
	vi A(N); re(A);
	int sm = SUM(A);
	FOR(i,N - 1) A.pb(A[i]);
	int n = N;
	N = sz(A);
	multiset<int>m;
	int ans = 0;
	F0R(i,1,N) A[i] += A[i - 1];
	
	int d = n / 2;
	//ps(A);
	for (int i = d - 1; i < n - 1;++i) m.ins(A[i] - (i >= d ? A[i - d] : 0));
	//trav(x,m) cout << x << ' ';
	//cout << '\n' << "NU";
	for(int i = 0; i <= N - n;++i){
		//ps(A[i + d - 1] - (i ? A[i - 1] : 0),A[i + n - 1] - A[i + n - d - 1],i,d,n);
		m.erase(m.find(A[i + d - 1] - (i ? A[i - 1] : 0)));
		m.ins(A[i + n - 1] - A[i + n - d - 1]);
		ckmax(ans,sm - *--m.end());
		//trav(x,m) cout << x << ' ';
		//cout << '\n';
		//ps(*--m.end());
		}
	ps(ans);
}		 
main()
{   setIO();
	solve();
}
// look out for out of bounds arrays
// And more importantly, is y a vowel? Damian:1
// <3 :L ._. <_<
// You have no idea how high I can fly

Compilation message (stderr)

hac.cpp:369:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
  369 | main()
      | ^~~~
hac.cpp: In function 'void setF(std::string)':
hac.cpp:252:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  252 |   freopen((fileName+".in").c_str(), "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
hac.cpp:253:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  253 |   freopen((fileName+".out").c_str(), "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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