//Never stop trying
/*#pragma GCC target ("avx2")
#pragma GCC optimize ("Ofast")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")*/
#include "bits/stdc++.h"
using namespace std;
#define boost ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
typedef long long ll;
typedef string str;
typedef double db;
typedef long double ld;
typedef pair<int, int> pi;
#define fi first
#define se second
typedef vector<int> vi;
typedef vector<pi> vpi;
typedef vector<str> vs;
typedef vector<ld> vd;
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define endl "\n"
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
const int MOD = 1e9 + 7; //998244353
const ll INF = 2e9;
const int MX = 2e5 + 10;
const int nx[4] = {0, 0, 1, -1}, ny[4] = {1, -1, 0, 0}; //right left down up
template<class T> using V = vector<T>;
template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
ll cdiv(ll a, ll b) { return a / b + ((a ^ b) > 0 && a % b); } // divide a by b rounded up
//constexpr int log2(int x) { return 31 - __builtin_clz(x); } // floor(log2(x))
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
//mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
ll random(ll a, ll b){
return a + rng() % (b - a + 1);
}
#ifndef LOCAL
#define cerr if(false) cerr
#endif
#define dbg(x) cerr << #x << " : " << x << endl;
#define dbgs(x,y) cerr << #x << " : " << x << " / " << #y << " : " << y << endl;
#define dbgv(v) cerr << #v << " : " << "[ "; for(auto it : v) cerr << it << ' '; cerr << ']' << endl;
#define here() cerr << "here" << endl;
void IO() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
}
#ifndef LOCAL
#include "towns.h"
#endif
int NN,N;
vpi adjj[200];
int dis[200];
void dfs2(int u){
for(auto v: adjj[u]){
if(dis[v.fi]==-1){
dis[v.fi]=dis[u]+v.se;
dfs2(v.fi);
}
}
}
#ifdef LOCAL
int getDistance(int u, int v){
FOR(i,0,NN) dis[i]=-1;
dis[u]=0;
dfs2(u);
return dis[v];
}
#endif
int cntt;
bool vis[200];
vi adj[200];
void dfs(int u){
//dbg(u)
cntt++;
vis[u]=true;
for(auto v: adj[u]) if(!vis[v]) dfs(v);
}
int hubDistance(int N, int sub){
::N=N;
int dist[N][N];
FOR(i,0,N) dist[i][i]=0;
int diam=-1,U,V;
FOR(i,0,N) FOR(j,i+1,N){
dist[i][j]=dist[j][i]=getDistance(i,j);
if(ckmax(diam,dist[i][j])) U=i,V=j;
}
int R=INF;
vpi vec;
vi depth(N,0);
FOR(i,0,N){
int a=diam,b=dist[i][U],c=dist[i][V];
int x=(a+b-c)/2,y=(a-b+c)/2,z=(-a+b+c)/2;
depth[i]=z;
vec.eb(x,i);
ckmin(R,max(x,y));
}
sort(all(vec));
//for(auto x: vec) cout << x.fi << ' ' << x.se << endl;
vpi hubs;
int cnt=0;
FOR(i,0,sz(vec)){
if(i && vec[i].fi==vec[i-1].fi) cnt++;
else{
if(cnt) hubs.eb(vec[i-1].fi,cnt);
cnt=1;
}
}
if(cnt>0) hubs.eb(vec[N-1].fi,cnt);
sort(all(hubs));
//for(auto x: hubs) cout << x.fi << ' ' << x.se << endl;
int found=-1,pref=0;
for(auto x: hubs){
if(max(x.fi,diam-x.fi)==R){
if(max(pref,N-pref-x.se)<=N/2) found=x.fi;
}
pref+=x.se;
}
//dbg(found)
if(found==-1) R=-R;
else{
vi v;
for(auto x: vec) if(x.fi==found) v.pb(x.se);
//dbgv(v)
FOR(i,0,N) vis[i]=false,adj[i].clear();
FOR(i,0,sz(v)) FOR(j,i+1,sz(v)){
if(dist[v[i]][v[j]]!=depth[v[i]]+depth[v[j]]){
adj[v[i]].pb(v[j]);
adj[v[j]].pb(v[i]);
}
}
/*FOR(i,0,N){
for(auto x: adj[i]) cout << x << ' ' ; cout << endl;
}*/
for(auto u: v) if(!vis[u]){
cntt=0;
dfs(u);
if(cntt>N/2){
R=-R;
break;
}
dbg(cntt)
}
}
return R;
}
#ifdef LOCAL
int main() {
boost; IO();
cin>>NN>>N;
FOR(i,0,NN-1){
int u,v,w; cin>>u>>v>>w;
adjj[u].eb(v,w);
adjj[v].eb(u,w);
}
cout << hubDistance(N,0) << endl;
return 0;
}
#endif
/* Careful!!!
.Array bounds
.Infinite loops
.Uninitialized variables / empty containers
.Multisets are shit
Some insights:
.Binary search
.Graph representation
.Write brute force code
.Change your approach
*/
Compilation message
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:103:31: warning: declaration of 'N' shadows a global declaration [-Wshadow]
103 | int hubDistance(int N, int sub){
| ^
towns.cpp:70:8: note: shadowed declaration is here
70 | int NN,N;
| ^
towns.cpp:103:28: warning: unused parameter 'sub' [-Wunused-parameter]
103 | int hubDistance(int N, int sub){
| ~~~~^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
20 ms |
492 KB |
Output is correct |
| 2 |
Correct |
17 ms |
492 KB |
Output is correct |
| 3 |
Correct |
1 ms |
364 KB |
Output is correct |
| 4 |
Correct |
24 ms |
492 KB |
Output is correct |
| 5 |
Correct |
23 ms |
492 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
364 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
17 ms |
492 KB |
Output is correct |
| 2 |
Correct |
24 ms |
1004 KB |
Output is correct |
| 3 |
Correct |
1 ms |
364 KB |
Output is correct |
| 4 |
Correct |
24 ms |
1004 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
364 KB |
Output isn't correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
364 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
364 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
