mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-12-25 21:34:59 +00:00
209 lines
3.8 KiB
C++
209 lines
3.8 KiB
C++
#include <iostream>
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#include <stack>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1e6 + 5;
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int n, k, c[N], cnt, ans = 0x3f3f3f3f;
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int id[N], rid[N], fa[N], dep[N], siz[N], son[N], top[N];
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std::vector<int> g[N], g2[N], pos[N];
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int dfn[N], low[N], scc_cnt, scc_id[N];
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int res_siz[N], deg[N];
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std::stack<int> st;
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bool vis[N];
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struct node {
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int l, r;
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node(const int &_l = 0, const int &_r = 0)
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: l(_l), r(_r) {}
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} tr[N << 2];
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void dfs1(int u, int f) {
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fa[u] = f;
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dep[u] = dep[f] + 1;
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siz[u] = 1;
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for (int v : g[u]) {
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if (v == f) continue;
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dfs1(v, u);
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siz[u] += siz[v];
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if (siz[son[u]] < siz[v]) son[u] = v;
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}
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}
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void dfs2(int u, int t) {
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static int cnt = 0;
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rid[id[u] = ++cnt] = u;
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top[u] = t;
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if (son[u]) dfs2(son[u], t);
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for (int v : g[u]) {
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if (v == fa[u] || v == son[u]) continue;
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dfs2(v, v);
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}
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}
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void build(int u, int l, int r) {
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tr[u] = node(l, r);
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cnt++;
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if (l == r) {
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g2[k + u].emplace_back(c[rid[l]]);
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return;
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}
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int mid = (l + r) >> 1;
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build(u << 1, l, mid);
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build(u << 1 | 1, mid + 1, r);
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g2[k + u].emplace_back(k + (u << 1));
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g2[k + u].emplace_back(k + (u << 1 | 1));
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}
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void modify(int u, int l, int r, int x) {
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if (l <= tr[u].l && tr[u].r <= r) {
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g2[x].emplace_back(k + u);
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return;
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}
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int mid = (tr[u].l + tr[u].r) >> 1;
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if (l <= mid) modify(u << 1, l, r, x);
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if (r > mid) modify(u << 1 | 1, l, r, x);
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}
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void modify_path(int u, int v) {
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int x = c[u];
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while (top[u] != top[v]) {
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if (dep[top[u]] < dep[top[v]]) std::swap(u, v);
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modify(1, id[top[u]], id[u], x);
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u = fa[top[u]];
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}
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if (dep[v] > dep[u]) std::swap(u, v);
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modify(1, id[v], id[u], x);
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}
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void tarjan(int u) {
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static int cnt = 0;
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dfn[u] = low[u] = ++cnt;
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st.emplace(u);
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vis[u] = true;
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for (int v : g2[u]) {
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if (!dfn[v]) {
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tarjan(v);
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low[u] = std::min(low[u], low[v]);
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} else if (vis[v]) {
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low[u] = std::min(low[u], dfn[v]);
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}
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}
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if (dfn[u] == low[u]) {
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scc_cnt++;
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int v;
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do {
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v = st.top();
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st.pop();
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scc_id[v] = scc_cnt;
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vis[v] = false;
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} while (v != u);
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}
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}
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int lca(int u, int v) {
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while (top[u] != top[v]) {
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if (dep[top[u]] < dep[top[v]]) std::swap(u, v);
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u = fa[top[u]];
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}
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return dep[u] < dep[v] ? u : v;
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> k;
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for (int i = 1, x, y; i < n; i++) {
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cin >> x >> y;
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g[x].emplace_back(y);
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g[y].emplace_back(x);
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}
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for (int i = 1; i <= n; i++) {
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cin >> c[i];
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pos[c[i]].emplace_back(i);
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}
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dfs1(1, 1);
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dfs2(1, 1);
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build(1, 1, n);
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for (int i = 1; i <= k; i++) {
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if (pos[i].size() <= 1) continue;
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int p = pos[i][0];
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for (int j = 1; j < pos[i].size(); j++) {
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int l = lca(pos[i][0], pos[i][j]);
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if (l != pos[i][j]) modify_path(pos[i][j], l);
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if (dep[l] < dep[p]) p = l;
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}
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if (p != pos[i][0]) {
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modify_path(pos[i][0], p);
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}
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}
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for (int i = 1; i <= k + cnt; i++) {
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if (!dfn[i]) tarjan(i);
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}
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for (int i = 1; i <= k; i++) {
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res_siz[scc_id[i]]++;
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}
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for (int i = 1; i <= k + cnt; i++) {
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for (int v : g2[i]) {
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if (scc_id[i] != scc_id[v]) {
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deg[scc_id[i]]++;
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}
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}
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}
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for (int i = 1; i <= k; i++) {
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if (deg[scc_id[i]] == 0) {
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ans = std::min(ans, res_siz[scc_id[i]] - 1);
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}
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}
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cout << ans << endl;
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return 0;
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}
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