Submission #216894

#	Time	Username	Problem	Language	Result	Execution time	Memory
216894		eriksuenderhauf	Capital City (JOI20_capital_city)	C++11	100 / 100	282 ms	61788 KiB

capital_city

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define trav(x,a) for (const auto& x: a)
#define sz(x) (int)(x).size()
#define mem(a,v) memset((a), (v), sizeof (a))
#define enl printf("\n")
#define case(t) printf("Case #%d: ", (t))
#define ni(n) scanf("%d", &(n))
#define nl(n) scanf("%I64d", &(n))
#define nai(a, n) for (int _i = 0; _i < (n); _i++) ni(a[_i])
#define nal(a, n) for (int _i = 0; _i < (n); _i++) nl(a[_i])
#define pri(n) printf("%d\n", (n))
#define prl(n) printf("%I64d\n", (n))
#define pii pair<int, int>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vll vector<pll>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define mp make_pair
#define st first
#define nd second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<int,int,hash<int>> ht;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> oset;
const double pi = acos(-1);
const int mod = 1e9 + 7;
const int inf = 1e9 + 7;
const int N = 1e6 + 5;
const double eps = 1e-9;

#define log2(x) (31 - __builtin_clz(x))

struct sparse_table {
  int n;
  vector<int> a;
  vector<vector<int>> st;
  int combine(int dl, int dr) {
    return a[dl] > a[dr] ? dl : dr;
  }
  sparse_table() {}
  sparse_table(vector<int> & a) : n(a.size()), a(a), st(log2(n) + 1, vector<int>(n)) {
    for (int i = 0; i < n; i++)
      st[0][i] = i;
    for (int j = 1; 1 << j <= n; j++)
      for (int i = 0; i + (1 << j) <= n; i++)
        st[j][i] = combine(st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);
  }
  // query the data on the range [l, r[
  int query(int l, int r) {
    int s = log2(r - l);
    return combine(st[s][l], st[s][r - (1 << s)]);
  }
};

struct lowest_common_ancestor {
  int n, m = 0;
  vector<int> a, v, h, par;
  vector<vector<int>>& e;
  sparse_table st;
  lowest_common_ancestor(vector<vector<int>> & e, int r) : n(e.size()), a(n), v(2 * n - 1), h(2 * n - 1), e(e), par(n) {
    dfs(r);
    st = sparse_table(h);
  }
  void dfs(int i, int p = -1, int d = 0) {
    par[i] = p;
    a[i] = m; v[m] = i; h[m++] = d;
    for (int j : e[i]) {
      if (j == p)
        continue;
      dfs(j, i, d - 1);
      v[m] = i; h[m++] = d;
    }
  }
  // calculate the lowest common ancestor of x and y
  int lca(int x, int y) {
    return v[st.query(min(a[x], a[y]), max(a[x], a[y]) + 1)];
  }
  int ok(int x, int y) {
    return lca(par[x], y) == y;
  }
};

struct strongly_connected_components {
  int n, v = 0, c = 0;
  vector<bool> ins;
  vector<int> s, num, low, com, cnt;
  vector<vector<int>>& e;
  strongly_connected_components(vector<vector<int>> & e) : n(e.size()), ins(n), num(n, -1), low(n), com(n), e(e), cnt(n) {
    for (int i = 0; i < n; i++)
      if (num[i] == -1)
        dfs(i);
    for (int i = 0; i < n; i++)
      trav(x, e[i])
        if (com[x] != com[i])
          cnt[com[i]] = n+1;
  }
  // use commented lines for biconnected components in undirected graphs
  void dfs(int i) {
  // void dfs(int i, int p = -1) {
    num[i] = low[i] = v++;
    s.push_back(i); ins[i] = true;
    for (int j : e[i]) {
      // if (j == p) {
      //   p = -1;
      //   continue;
      // }
      if (num[j] == -1)
        dfs(j);
        // dfs(j, i);
      if (ins[j])
        low[i] = min(low[i], low[j]);
    }
    if (low[i] == num[i]) {
      int j;
      do {
        j = s.back(); s.pop_back(); ins[j] = false;
        com[j] = c;
        cnt[c]++;
      } while (j != i);
      c++;
    }
  }
};


int en[N], c[N];
// vector<int> st[N], adj[N];
vector<vector<int>> e;

int main() {
  int n, k; scanf("%d %d", &n, &k);
  e.resize(n);
  for (int i = 1, u, v; i < n; i++) {
    scanf("%d %d", &u, &v); u--, v--;
    e[u].push_back(v);
    e[v].push_back(u);
  }
  for (int i = 0; i < n; i++) {
    scanf("%d", &c[i]); c[i]--;
    en[c[i]] = i;
  }
  lowest_common_ancestor l(e, 0);
  for (int i = 0; i < n; i++)
    en[c[i]] = l.lca(en[c[i]], i);
  vector<vector<int>> f(k);
  for (int i = 0; i < n; i++) {
    if (l.par[i] != -1 && c[i] != c[l.par[i]] && l.ok(i, en[c[i]])) {
      f[c[i]].pb(c[l.par[i]]);
      // cout << c[i]+1 << " " << c[l.par[i]]+1 << endl;
    }
  }
  strongly_connected_components sc(f);
  int ans = k-1;
  for (int i = 0; i < sc.c; i++)
    ans = min(ans, sc.cnt[i] - 1);
  printf("%d\n", ans);
  return 0;
}

Compilation message (stderr)

capital_city.cpp: In constructor 'lowest_common_ancestor::lowest_common_ancestor(std::vector<std::vector<int> >&, int)':
capital_city.cpp:64:24: warning: 'lowest_common_ancestor::e' will be initialized after [-Wreorder]
   vector<vector<int>>& e;
                        ^
capital_city.cpp:63:24: warning:   'std::vector<int> lowest_common_ancestor::par' [-Wreorder]
   vector<int> a, v, h, par;
                        ^~~
capital_city.cpp:66:3: warning:   when initialized here [-Wreorder]
   lowest_common_ancestor(vector<vector<int>> & e, int r) : n(e.size()), a(n), v(2 * n - 1), h(2 * n - 1), e(e), par(n) {
   ^~~~~~~~~~~~~~~~~~~~~~
capital_city.cpp: In constructor 'strongly_connected_components::strongly_connected_components(std::vector<std::vector<int> >&)':
capital_city.cpp:93:24: warning: 'strongly_connected_components::e' will be initialized after [-Wreorder]
   vector<vector<int>>& e;
                        ^
capital_city.cpp:92:33: warning:   'std::vector<int> strongly_connected_components::cnt' [-Wreorder]
   vector<int> s, num, low, com, cnt;
                                 ^~~
capital_city.cpp:94:3: warning:   when initialized here [-Wreorder]
   strongly_connected_components(vector<vector<int>> & e) : n(e.size()), ins(n), num(n, -1), low(n), com(n), e(e), cnt(n) {
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
capital_city.cpp: In function 'int main()':
capital_city.cpp:137:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int n, k; scanf("%d %d", &n, &k);
             ~~~~~^~~~~~~~~~~~~~~~~
capital_city.cpp:140:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &u, &v); u--, v--;
     ~~~~~^~~~~~~~~~~~~~~~~
capital_city.cpp:145:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &c[i]); c[i]--;
     ~~~~~^~~~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 10 / 10
• Subtask 3: 30 / 30
• Subtask 4: 59 / 59