Submission #95456

#	Time	Username	Problem	Language	Result	Execution time	Memory
95456		forestryks	Printed Circuit Board (CEOI12_circuit)	C++14	5 / 100	1080 ms	4344 KiB

circuit

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

#define mp make_pair
#define pb push_back
#define FAST_IO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define FILE_IO(x) freopen((string(x) + ".in").c_str(), "r", stdin); freopen((string(x) + ".out").c_str(), "w", stdout)
#define f first
#define s second
#define x1 x1qwer
#define y1 y1qwer
#define right right123
#define left left123
#define foreach(it, v) for (auto it : v)
#define rep(it, n) for (int it = 0; it < n; ++it)
#define forin(it, l, r) for (int it = l; it < r; ++it)
#define all(x) x.begin(), x.end()

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const double DINF = numeric_limits<double>::infinity();
const ll MOD = 1e9 + 7;
const double EPS = 1e-7;
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
mt19937 mmtw_(MOD);
uniform_int_distribution<ll> rd_;
ll randomll() { return rd_(mmtw_);}
ll rnd(ll x, ll y) { return rd_(mmtw_) % (y - x + 1) + x; }
////////////////////////////////////////////////////////////////////////////////////////////////

struct pt {
    int x, y;
    int id;
};

inline pt operator-(const pt &a) {
    return {-a.x, -a.y};
}

inline pt operator-(const pt &a, const pt &b) {
    return {a.x - b.x, a.y - b.y};
}

inline ll dot(const pt &a, const pt &b) {
    return 1LL * a.x * b.x + 1LL * a.y * b.y;
}

inline ll cross(const pt &a, const pt &b) {
    return 1LL * a.x * b.y - 1LL * a.y * b.x;
}

inline ll dd0(const pt &a) {
    return dot(a, a);
}

const int MAXN = 1e5 + 5;
int n;
pt a[MAXN];

inline int md(int x) {
    if (x >= n) return x - n;
    if (x < 0) return x + n;
    return x;
}

int findLowest() {
    int s = 0;
    for (int i = 0; i < n; ++i) {
        ll cr = cross(a[i], a[s] - a[i]);
        if (cr > 0 || (cr == 0 && dd0(a[i]) < dd0(a[s]))) {
            s = i;
        }
    }
    return s;
}

int findHighest() {
    int t = 0;
    for (int i = 0; i < n; ++i) {
        ll cr = cross(a[i], a[t] - a[i]);
        if (cr < 0 || (cr == 0 && dd0(a[i]) < dd0(a[t]))) {
            t = i;
        }
    }
    return t;
}

struct seg {
    pt a, b;
};
seg s[MAXN];

bool inter(const pt &a, const seg &b) {
    if (!(cross(a, b.b) >= 0 && cross(a, b.a) <= 0)) return false;
    if (!(cross(b.b - b.a, a - b.a) <= 0 && cross(b.b - b.a, -b.a) >= 0)) return false;
    return true;
}

bool check(const pt &a, int sg) {
    for (int i = 0; i < n; ++i) {
        if (i == sg) continue;
        if (inter(a, s[i])) return false;
    }
    return true;
}

vector<int> solve() {
    vector<int> res;

    for (int i = 0; i < n; ++i) {
        if (check(s[i].a, i)) res.push_back(s[i].a.id);
        if (check(s[i].b, i)) res.push_back(s[i].b.id);
    }

    sort(all(res));
    res.erase(unique(all(res)), res.end());
    return res;
}

int main() {
    FAST_IO;
    cin >> n;
    rep(i, n) {
        cin >> a[i].x >> a[i].y;
        a[i].id = i + 1;
    }

    assert(n > 2);

    int lowest = findLowest();
    if (cross(a[md(lowest - 1)] - a[lowest], a[md(lowest + 1)] - a[lowest]) < 0) {
        reverse(a, a + n);
    }

    rotate(a, a + findLowest(), a + n);
    n = findHighest() + 1;

    int sz = 0;
    for (int i = 0; i + 1 < n; ++i) {
        if (cross(a[i], a[i + 1] - a[i]) > 0) s[sz++] = {a[i], a[i + 1]};
    }
    n = sz;

    vector<int> ans = solve();

    cout << ans.size() << '\n';
    for (auto it : ans) {
        cout << it << ' ';
    } cout << '\n';
}

• Subtask 1: 5 / 100