Submission #749634

#	Time	Username	Problem	Language	Result	Execution time	Memory
749634		stevancv	Capital City (JOI20_capital_city)	C++14	100 / 100	368 ms	87116 KiB

capital_city

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 2e5 + 2;
const int inf = 1e9;
vector<int> g[N];
int par[N][18], in[N], out[N], tsz;
void Dfs(int s, int e) {
    in[s] = ++tsz;
    par[s][0] = e;
    for (int i = 1; i < 18; i++) par[s][i] = par[par[s][i - 1]][i - 1];
    for (int u : g[s]) {
        if (u == e) continue;
        Dfs(u, s);
    }
    out[s] = tsz;
}
bool Ancestor(int u, int v) {
    return in[u] <= in[v] && out[v] <= out[u];
}
int Lca(int u, int v) {
    if (Ancestor(u, v)) return u;
    if (Ancestor(v, u)) return v;
    for (int i = 17; i >= 0; i--) {
        if (par[u][i] && !Ancestor(par[u][i], v)) u = par[u][i];
    }
    return par[u][0];
}
int c[N], predak[N];
vector<int> boja[N];
set<int> koji[N];
void Dfs1(int s, int e) {
    for (int u : g[s]) {
        if (u == e) continue;
        if (c[s] != c[u] && Ancestor(predak[c[u]], s)) koji[c[u]].insert(c[s]);
        Dfs1(u, s);
    }
}
vector<int> a[N], b[N], order;
int visited[N], id[N], szk[N], brk;
void Dfs2(int s) {
    if (visited[s] == 1) return;
    visited[s] = 1;
    for (int u : a[s]) {
        Dfs2(u);
    }
    order.push_back(s);
}
void Dfs3(int s) {
    if (id[s] > 0) return;
    id[s] = brk;
    szk[brk] += 1;
    for (int u : b[s]) {
        Dfs3(u);
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, k;
    cin >> n >> k;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    Dfs(1, 0);
    for (int i = 1; i <= n; i++) {
        cin >> c[i];
        boja[c[i]].push_back(i);
    }
    for (int i = 1; i <= k; i++) {
        predak[i] = boja[i][0];
        for (int j = 1; j < boja[i].size(); j++) predak[i] = Lca(predak[i], boja[i][j]);
    }
    Dfs1(1, 0);
    for (int i = 1; i <= k; i++) {
        for (int j : koji[i]) {
            a[i].push_back(j);
            b[j].push_back(i);
        }
    }
    for (int i = 1; i <= k; i++) {
        if (visited[i] == 0) {
            Dfs2(i);
        }
    }
    reverse(order.begin(), order.end());
    for (int i : order) {
        if (id[i] == 0) {
            brk += 1;
            Dfs3(i);
        }
    }
    vector<int> cnt(brk + 1);
    for (int i = 1; i <= k; i++) {
        for (int j : a[i]) {
            if (id[i] != id[j]) {
                cnt[id[i]] += 1;
            }
        }
    }
    int ans = inf;
    for (int i = 1; i <= brk; i++) if (cnt[i] == 0) smin(ans, szk[i] - 1);
    cout << ans << en;
    return 0;
}

Compilation message (stderr)

capital_city.cpp: In function 'int main()':
capital_city.cpp:81:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   81 |         for (int j = 1; j < boja[i].size(); j++) predak[i] = Lca(predak[i], boja[i][j]);
      |                         ~~^~~~~~~~~~~~~~~~

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