Submission #379693

#	Time	Username	Problem	Language	Result	Execution time	Memory
379693		VROOM_VARUN	Mergers (JOI19_mergers)	C++14	0 / 100	123 ms	26588 KiB

mergers

/*
ID: varunra2
LANG: C++
TASK: mergers
*/

#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif

#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second

const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions

int n, k;

VVI adj;
VII edg;
VI color;
VVI nodes;
VI dep;
VI par;
VI mx;
VI deg;

void init() {
  adj.resize(n);
  color.resize(n);
  nodes.resize(k);
  dep.resize(n);
  mx.resize(n);
  deg.assign(n, 0);
}

struct lca {
  const int bits = 20;
  VVI lft;
  VI tin;
  VI tout;
  int tmr = 0;

  void dfs(int u, int v) {
    tin[u] = tmr++;
    lft[u][0] = v;
    for (int i = 1; i < bits; i++) {
      int to = lft[u][i - 1];
      if (to == -1)
        lft[u][i] = -1;
      else
        lft[u][i] = lft[to][i - 1];
    }
    trav(x, adj[u]) {
      if (x == v) continue;
      dfs(x, u);
    }
    tout[u] = tmr++;
  }

  void init() {
    tin.resize(n);
    tout.resize(n);
    lft.resize(n);
    trav(x, lft) x.resize(bits);
    dfs(0, 1);
  }

  bool isAnc(int u, int v) {
    if (u == -1) return true;
    if (v == -1) return false;
    return tin[u] <= tin[v] and tout[u] >= tout[v];
  }

  int getLCA(int u, int v) {
    if (isAnc(u, v)) return u;
    if (isAnc(v, u)) return v;
    for (int i = bits - 1; i >= 0; i--) {
      if (!isAnc(lft[u][i], v)) {
        u = lft[u][i];
      }
    }
    return lft[u][0];
  }

  int getKthAnc(int u, int k) {
    for (int i = bits - 1; i >= 0; i--) {
      if (k & (1 << i)) {
        u = lft[u][i];
      }
    }
    return u;
  }
} lcaa;

void dfs_dep(int u, int v) {
  if (v == -1) dep[u] = 0;
  trav(x, adj[u]) {
    if (x == v) continue;
    dep[x] = dep[u] + 1;
    dfs_dep(x, u);
  }
}

void dfs_mx(int u, int v) {
  trav(x, adj[u]) {
    if (x == v) continue;
    dfs_mx(x, u);
    mx[u] = min(mx[u], mx[x]);
  }
}

int main() {
  // #ifndef ONLINE_JUDGE
  // freopen("mergers.in", "r", stdin);
  // freopen("mergers.out", "w", stdout);
  // #endif
  cin.sync_with_stdio(0);
  cin.tie(0);

  cin >> n >> k;

  if (n == 1) {
    cout << "0\n";
    return 0;
  }

  init();

  for (int i = 0; i < n - 1; i++) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    adj[u].PB(v);
    adj[v].PB(u);
    edg.PB(MP(u, v));
  }

  for (int i = 0; i < n; i++) {
    int col;
    cin >> col;
    col--;
    nodes[col].PB(i);
    color[i] = col;
  }

  dfs_dep(0, -1);
  mx = dep;
  lcaa.init();

  for (int i = 0; i < k; i++) {
    int pt = nodes[i][0];
    for (int j = 1; j < sz(nodes[i]); j++) {
      int u = pt;
      int v = nodes[i][j + 1];
      int lca = lcaa.getLCA(u, v);
      pt = lca;
      int val = dep[lca];
    }
    for (int j = 0; j < sz(nodes[i]); j++) {
      mx[nodes[i][j]] = min(mx[nodes[i][j]], dep[pt]);
    }
  }

  dfs_mx(0, -1);

  trav(x, edg) {
    int u = lcaa.getKthAnc(x.x, dep[x.x] - mx[x.x]);
    int v = lcaa.getKthAnc(x.y, dep[x.y] - mx[x.y]);
    if (u != v) {
      deg[u]++;
      deg[v]++;
    }
  }

  int ret = 0;

  for (int i = 0; i < n; i++) {
    if (deg[i] == 1) ret++;
  }

  cout << (ret + 1) / 2 << '\n';

  return 0;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:196:11: warning: unused variable 'val' [-Wunused-variable]
  196 |       int val = dep[lca];
      |           ^~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 24
• Subtask 3: 0 / 14
• Subtask 4: 0 / 22
• Subtask 5: 0 / 30