| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 391609 | usachevd0 | Towns (IOI15_towns) | C++14 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#ifndef DEBUG
#include "towns.h"
#endif
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define all(a) (a).begin(), (a).end()
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
using ld = long double;
template<typename T1, typename T2> bool chkmin(T1 &x, T2 y) { return y < x ? (x = y, true) : false; }
template<typename T1, typename T2> bool chkmax(T1 &x, T2 y) { return y > x ? (x = y, true) : false; }
void debug_out() { cerr << endl; }
template<typename T1, typename... T2> void debug_out(T1 A, T2... B) { cerr << ' ' << A; debug_out(B...); }
template<typename T> void mdebug_out(T* a, int n) { for (int i = 0; i < n; ++i) cerr << a[i] << ' '; cerr << endl; }
#ifdef DEBUG
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define mdebug(a, n) cerr << #a << ": ", mdebug_out(a, n)
#else
#define debug(...) 1337
#define mdebug(a, n) 1337
#endif
template<typename T> ostream& operator << (ostream& stream, const vector<T> &v) { for (auto x : v) stream << x << ' '; return stream; }
template<typename T1, typename T2> ostream& operator << (ostream& stream, const pair<T1, T2>& p) { return stream << p.first << ' ' << p.second; }
#ifdef DEBUG
int n;
int dist[110][110];
int getDistance(int i, int j) {
return dist[i][j];
}
#endif
int hubDistance(int n, int __) {
mt19937 rng(228);
auto get_all_from = [&](int v) -> vector<int> {
vector<int> d(n, 0);
for (int u = 0; u < n; ++u) {
if (u != v) {
d[u] = getDistance(v, u);
}
}
return d;
};
auto d0 = get_all_from(0);
int v1 = max_element(all(d0)) - d0.begin();
auto d1 = get_all_from(v1);
int v2 = max_element(all(d1)) - d1.begin();
int D = d1[v2];
auto d2 = get_all_from(v2);
vector<int> d = {0, D};
vector<int> dc(n), cx(n);
dc[v1] = 0;
dc[v2] = D;
cx[v1] = cx[v2] = 0;
for (int x = 0; x < n; ++x) {
if (x != v1 && x != v2) {
cx[x] = (d1[x] + d2[x] - D) / 2;
dc[x] = d1[x] - cx[x];
d.push_back(dc[x]);
}
}
sort(all(d));
vector<int> cnt;
vector<int> nd;
for (int x : d) {
if (nd.empty() || nd.back() < x) {
nd.push_back(x);
cnt.push_back(1);
} else {
++cnt.back();
}
}
swap(d, nd);
vector<int> pref_c(cnt.size() + 1, 0);
for (int i = 0; i < cnt.size(); ++i) {
pref_c[i + 1] = pref_c[i] + cnt[i];
}
vector<int> suf_c(cnt.size() + 1, 0);
for (int i = (int)cnt.size() - 1; i >= 0; --i) {
suf_c[i] = suf_c[i + 1] + cnt[i];
}
int R = 1e9;
for (int i = 0; i < d.size(); ++i) {
chkmin(R, max(d[i], D - d[i]));
}
bool found = false;
if (__ >= 3) for (int i = 0; i < d.size(); ++i) {
if (max(d[i], D - d[i]) == R && max(pref_c[i], suf_c[i + 1]) <= n / 2) {
if (cnt[i] <= n / 2) {
found = true;
break;
} else {
// once
vector<int> h;
for (int x = 0; x < n; ++x) {
if (x != v1 && x != v2 && dc[x] == d[i]) {
h.push_back(x);
}
}
vector<int> comp(n, -1);
int C = 0;
bool bad = false;
for (int x : h) {
if (comp[x] == -1) {
comp[x] = C++;
int sz = 1;
for (int y : h) {
if (comp[y] == -1 && getDistance(x, y) < cx[x] + cx[y]) {
++sz;
comp[y] = comp[x];
}
}
if (sz > n / 2) {
bad = true;
break;
}
rem -= sz;
}
}
if (!bad) {
found = true;
break;
}
/*bool bad = false;
for (int itr = 0; itr < 2e9; ++itr) {
if (h.size() <= n / 2) {
break;
}
int x = h[(rng() % h.size() + h.size()) % h.size()];
int sz = 0;
vector<int> new_h;
for (int y : h) {
if (x == y || getDistance(x, y) < cx[x] + cx[y]) {
++sz;
} else {
new_h.push_back(y);
}
}
if (sz > n / 2) {
bad = true;
break;
} else {
swap(h, new_h);
}
}
if (!bad) {
found = true;
break;
}*/
}
}
}
if (found) {
return R;
} else {
return -R;
}
}
#ifdef DEBUG
signed main() {
#ifdef DEBUG
freopen("towns.in", "r", stdin);
#endif
ios::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
cin >> dist[i][j];
}
}
cout << hubDistance(n, 1) << '\n';
return 0;
}
#endif