#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
vector<vector<int>> f(n, vector<int>(n));
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
cin >> f[i][j];
}
}
map<pair<int, int>, int> mp;
auto Ask = [&](int l, int r) {
if (l > r) {
swap(l, r);
}
if (l == r) {
return 0;
}
if (mp.count({l, r})) {
return mp[{l, r}];
}
return (int) f[l][r];
//mp[{l, r}] = getDistance(l, r);
return mp[{l, r}];
};
int x = 0, y = 0;
for (int i = 1; i < n; i++) {
if (Ask(0, i) > Ask(0, x)) {
x = i;
}
}
for (int i = 0; i < n; i++) {
if (Ask(x, i) > Ask(x, y)) {
y = i;
}
}
vector<int> d;
vector<int> my(n);
for (int i = 0; i < n; i++) {
my[i] = (Ask(i, x) - Ask(i, 0) + Ask(0, x)) / 2;
d.push_back(my[i]);
}
sort(d.begin(), d.end());
d.erase(unique(d.begin(), d.end()), d.end());
int sz = (int) d.size();
vector<int> r(sz);
for (int i = 0; i < sz; i++) {
r[i] = max(d[i], Ask(x, y) - d[i]);
}
int mn = *min_element(r.begin(), r.end());
vector<int> cnt(sz);
for (int i = 0; i < n; i++) {
int idx = (int) (lower_bound(d.begin(), d.end(), my[i]) - d.begin());
cnt[idx] += 1;
}
vector<int> pref(sz);
for (int i = 0; i < sz; i++) {
if (i > 0) {
pref[i] = pref[i - 1];
}
pref[i] += cnt[i];
}
vector<int> cands;
for (int i = 1; i + 1 < sz; i++) {
if (r[i] == mn && max((i == 0 ? 0 : pref[i - 1]), pref[sz - 1] - pref[i]) <= n / 2) {
cands.push_back(i);
}
}
if ((int) cands.size() == 0) {
cout << -mn << '\n';
return 0;
}
if ((int) cands.size() == 2) {
cout << mn << '\n';
return 0;
}
auto Solve = [&](int h) {
vector<int> ids(n);
iota(ids.begin(), ids.end(), 0);
vector<int> par(n);
iota(par.begin(), par.end(), 0);
vector<int> sz(n, 1);
function<int(int)> Get = [&](int x) {
return par[x] == x ? x : par[x] = Get(par[x]);
};
auto Merge = [&](int a, int b) {
a = Get(a);
b = Get(b);
if (a == b) {
return;
}
par[b] = a;
sz[a] += sz[b];
};
auto Diff = [&](int a, int b) {
if ((my[a] == d[h]) != (my[b] == d[h])) {
return true;
}
if (my[a] != d[h]) {
return (my[a] < d[h]) != (my[b] < d[h]);
}
int d_a = Ask(a, x) - my[a];
int d_b = Ask(b, x) - my[b];
assert(d_a >= 0 && d_b >= 0);
assert(d_a + d_b >= Ask(a, b));
return d_a + d_b == Ask(a, b);
};
vector<int> vec;
while (ids.size() > 1) {
vector<int> new_ids;
for (int i = 0; i + 1 < (int) ids.size(); i += 2) {
if (Diff(ids[i], ids[i + 1])) {
// ...
} else {
Merge(ids[i], ids[i + 1]);
new_ids.push_back(ids[i]);
}
}
swap(ids, new_ids);
}
if (ids.empty()) {
return false;
}
int e = ids.back();
iota(par.begin(), par.end(), 0);
sz = vector<int>(n, 1);
for (int i = 0; i < n; i++) {
if (i != Get(i) || i == Get(e)) {
continue;
}
if (!Diff(i, e)) {
Merge(i, e);
}
}
return *max_element(sz.begin(), sz.end()) <= n / 2;
};
if (Solve(cands[0])) {
cout << mn << '\n';
} else {
cout << -mn << '\n';
}
return 0;
}
Compilation message
towns.cpp: In lambda function:
towns.cpp:87:17: warning: declaration of 'sz' shadows a previous local [-Wshadow]
87 | vector<int> sz(n, 1);
| ^~
towns.cpp:50:7: note: shadowed declaration is here
50 | int sz = (int) d.size();
| ^~
towns.cpp: In lambda function:
towns.cpp:88:38: warning: declaration of 'x' shadows a previous local [-Wshadow]
88 | function<int(int)> Get = [&](int x) {
| ~~~~^
towns.cpp:31:7: note: shadowed declaration is here
31 | int x = 0, y = 0;
| ^
/usr/bin/ld: /tmp/ccotyNfB.o: in function `main':
grader.c:(.text.startup+0x0): multiple definition of `main'; /tmp/ccSVvkUA.o:towns.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccotyNfB.o: in function `main':
grader.c:(.text.startup+0x83): undefined reference to `hubDistance(int, int)'
collect2: error: ld returned 1 exit status
