Submission #914196

#	Time	Username	Problem	Language	Result	Execution time	Memory
914196		mychecksedad	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	255 ms	101308 KiB

Main

/* Author : Mychecksdead  */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
const int N = 1e6+100, M = 1e5+10, K = 52, MX = 30;


ll dp[N], dep[N];
int _lca(int u, int v);
struct Dsu{
  vector<int> s, p, mx;
  Dsu(int n){
    s.resize(n+1, 1);
    p.resize(n+1);
    mx.resize(n+1);
    for(int i = 1; i <= n; ++i) p[i] = i, mx[i] = i;
  }
  int find(int v){
    if(p[v] == v) return v;
    return p[v] = find(p[v]);
  }
  void merge(int a, int b){
    int u = find(a);
    int v = find(b); // b is the bigger vertex
    if(u != v){
      // cout << a << ' ' << b << ' ' <<mx[u] << '\n';
      dp[b] = max(dp[b], dp[mx[u]] + dep[mx[u]] + dep[b] - 2 * dep[_lca(mx[u], b)]);
      if(s[u] < s[v]) swap(u, v);
      mx[u] = max(mx[v], mx[u]);
      p[v] = u;
      s[u] += s[v];
    }
  }
};


int n, a[N], timer=0, tin[N], tout[N], up[N][K];
vector<array<int, 2>> edges;
vector<int> g[N];

void dfs(int v, int p){
  dep[v] = dep[p] + 1;
  up[v][0] = p;
  tin[v] = timer++;
  for(int u: g[v]) if(u != p) dfs(u, v);
  tout[v] = timer++;
}
bool is(int u, int v){
  return tin[u] <= tin[v] && tout[v] <= tout[u];
}
int _lca(int u, int v){
  if(is(u, v)) return u;
  if(is(v, u)) return v;
  for(int j = K-1; j >= 0; --j) if(!is(up[u][j], v)) u = up[u][j];
  return up[u][0];
}

void solve(){
  cin >> n;
  for(int i = 1; i <= n; ++i) cin >> a[i];

  for(int i = 0; i < n-1; ++i){
    int u, v; cin >> u >> v;
    u = a[u], v = a[v];
    g[u].pb(v);
    g[v].pb(u);
    edges.pb({max(u, v), min(u, v)});
  }
  sort(all(edges));
  dep[1] = 0;
  dfs(1, 1);
  for(int j = 1; j < K; ++j) for(int i = 1; i <= n; ++i) up[i][j] = up[up[i][j - 1]][j - 1];

  Dsu d(n);

  for(auto e: edges){
    int u = e[0], v = e[1];
    // cout << u << ' ' << v << '\n';
    d.merge(v, u);
  }
  // for(int i = 1; i <= n; ++i) cout << dp[i] << ' ';


  cout << dp[n];
}



int main(){
  cin.tie(0); ios::sync_with_stdio(0);
  int tt = 1, aa;
  // freopen("in.txt", "r", stdin);
  // freopen("out.txt", "w", stdout);
  // cin >> tt;
  while(tt--){
    solve();
    en;
  }
  cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
  return 0;
} 

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:96:15: warning: unused variable 'aa' [-Wunused-variable]
   96 |   int tt = 1, aa;
      |               ^~

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26