Submission #1124474

#	Time	Username	Problem	Language	Result	Execution time	Memory
1124474		ljtunas	Odašiljači (COCI20_odasiljaci)	C++20	14 / 70	21 ms	328 KiB

odasiljaci

// author : anhtun_hi , nqg
// 25-26.12.2024

#include <bits/stdc++.h>
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define reset(h, v)    memset(h, v, sizeof h)
#define Forv(i, a)     for(auto& i : a)
#define For(i, a, b)   for(int i = a; i <= b; ++i)
#define Ford(i, a, b)  for(int i = a; i >= b; --i)
#define c_bit(i)     __builtin_popcountll(i)
#define Bit(mask, i)    ((mask >> i) & 1LL)
#define onbit(mask, i)  ((mask) bitor (1LL << i))
#define offbit(mask, i) ((mask) &~ (1LL << i))
#define Log2(x) (63 - __builtin_clzll(x))
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
using namespace std;

using ll = long long;
using ii = pair<ll, ll>;
using db = long double;
using ull = unsigned long long;

namespace std {
    template <typename T, int D>
    struct _vector : public vector <_vector <T, D - 1>> {
        static_assert(D >= 1, "Dimension must be positive!");
        template <typename... Args>
        _vector(int n = 0, Args... args) : vector <_vector <T, D - 1>> (n, _vector <T, D - 1> (args...)) {}
    };
    template <typename T> struct _vector <T, 1> : public vector <T> {
        _vector(int n = 0, const T& val = T()) : vector <T> (n, val) {}
    };
    template <class A, class B> bool minimize(A &a, B b){return a > b ? a = b, true : false;}
    template <class A, class B> bool maximize(A &a, B b){return a < b ? a = b, true : false;}
}
const int dx[] = {0, 0, +1, -1}, dy[] = {-1, +1, 0, 0}, LOG = 20, base = 311, inf = 1e9 + 5;
const int MAXN = 1e6 + 5;
const  ll  mod = 1e9 + 7;
const  ll   oo = 1e18;
const db esp = 1e-9;

#define int long long

int n;

struct disjoint_set{
    int par[MAXN];
    void init() {
        For(i, 1, n) par[i] = -1;
    }
    int find(int u) {
        return (par[u] < 0) ? u : (par[u] = find(par[u]));
    }
    bool merge(int u, int v) {
        u = find(u), v = find(v);
        if (u == v) return false;
        if (par[u] > par[v]) swap(u, v);
        par[u] += par[v], par[v] = u;
        return true;
    }
} dsu;

struct Point{
    ll x, y; int id;
} a[MAXN];

bool cmp1(const Point &u, const Point &v){
    return (u.x < v.x) || (u.x == v.x && u.y < v.y);
}

bool cmp2(const Point &u, const Point &v){
    return (u.y < v.y) || (u.y == v.y && u.x < v.x);
}

bool cmp3(const Point &u, const Point &v){
    return (u.x + u.y < v.x + v.y);
}

bool cmp4(const Point &u, const Point &v){
    return (u.x - u.y < v.x - v.y);
}

db sqr(ll x){return x * x;}

db kc(const Point &u, const Point &v){
    return sqrt(sqr(u.x-v.x) + sqr(u.y-v.y));
}

bool check(db val){
    dsu.init();
    sort(a + 1, a + n + 1, cmp1);
    For(i, 2, n){
        auto [ux, uy, u] = a[i];
        auto [vx, vy, v] = a[i - 1];
        if (kc(a[i], a[i - 1]) <= val) dsu.merge(u, v);
    }
    sort(a + 1, a + n + 1, cmp2);
    For(i, 2, n){
        auto [ux, uy, u] = a[i];
        auto [vx, vy, v] = a[i - 1];
        if (kc(a[i], a[i - 1]) <= val) dsu.merge(u, v);
    }
    sort(a + 1, a + n + 1, cmp3);
    For(i, 2, n){
        auto [ux, uy, u] = a[i];
        auto [vx, vy, v] = a[i - 1];
        if (kc(a[i], a[i - 1]) <= val) dsu.merge(u, v);
    }
    sort(a + 1, a + n + 1, cmp4);
    For(i, 2, n){
        auto [ux, uy, u] = a[i];
        auto [vx, vy, v] = a[i - 1];
        if (kc(a[i], a[i - 1]) <= val) dsu.merge(u, v);
    }
    int cnt = 0;
    For(i, 1, n) cnt += (dsu.find(i) == i);
    return (cnt == 1);
}

void Solve() {
    cin >> n;
    For(i, 1, n) {
        cin >> a[i].x >> a[i].y;
        a[i].id = i;
    }
    db l = 0, r = 1e12;
    while (abs(r - l) > esp){
        db mid = (l + r) / 2;
        if (check(mid)) r = mid;
        else l = mid;
    }
    db ans = r / 2;

    cout << setprecision(7) << fixed << ans << '\n';
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    if(fopen("COCI20_odasiljaci.inp", "r")) {
        freopen("COCI20_odasiljaci.inp", "r", stdin);
        freopen("COCI20_odasiljaci.out", "w", stdout);
    }

    int t = 1;
//    cin >> t;
    while(t --) Solve();
    return 0;
}

Compilation message (stderr)

odasiljaci.cpp: In function 'int main()':
odasiljaci.cpp:142:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  142 |         freopen("COCI20_odasiljaci.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
odasiljaci.cpp:143:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  143 |         freopen("COCI20_odasiljaci.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 14 / 70