Submission #1143005

#	Time	Username	Problem	Language	Result	Execution time	Memory
1143005		Persia	Capital City (JOI20_capital_city)	C++17	0 / 100	257 ms	193880 KiB

capital_city

#include <bits/stdc++.h>
#define bit(i, x) (x >> i & 1)
#define ll long long
const int N = 1e6 + 5;
const int mod = 998244353;
using namespace std;

int n, k;
vector<int> G[N];
int c[N];

// additional
vector<int> G2[4 * N];
int st[4 * N];
int c1;
vector<int> b[N];

// straight line
int root;
int a[N], m;

// scc
int num[4 * N], low[4 * N], cnt;
int col[4 * N], ct;
int val[4 * N];
int deg[4 * N];
vector<int> stk;

// result
int res;

void predfs(int u, int par) {
    a[++m] = c[u];
    for(int v : G[u]) if(v != par) predfs(v, u);
}

void addedge(int x, int y) {
    G2[x].push_back(y);

    // cerr << x << " " << y << "\n";
}

void build(int id, int l, int r) {
    st[id] = ++c1;
    if(l == r) {
        addedge(st[id], a[l]);
        return;
    }
    int mid = (l + r) / 2;
    build(id * 2, l, mid);
    build(id * 2 + 1, mid + 1, r);
    addedge(st[id], st[id * 2]);
    addedge(st[id], st[id * 2 + 1]);
}

void addedge2(int id, int l, int r, int u, int v, int x) {
    if(l > v || r < u) return;
    if(l >= u && r <= v) {
        addedge(x, st[id]);
        return;
    }
    int mid = (l + r) / 2;
    addedge2(id * 2, l, mid, u, v, x);
    addedge2(id * 2 + 1, mid + 1, r, u, v, x);
}

void dfs(int u) {
    num[u] = low[u] = ++cnt;
    stk.push_back(u);
    for(int v : G2[u]) if(!col[v]) {
        if(num[v]) low[u] = min(low[u], num[v]);
        else {
            dfs(v);
            low[u] = min(low[u], low[v]);
        }
    }
    if(num[u] == low[u]) {
        ct++;
        while(1) {
            int top = stk.back();
            stk.pop_back();
            col[top] = ct;
            val[ct] += (top <= k);
            if(top == u) break;
        }
    }
}

signed main(int argc, char* argv[]) {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> n >> k;
    for(int i = 1; i < n; i++) {
        int x, y; cin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    for(int i = 1; i <= n; i++) cin >> c[i];

    // assert testcase
    for(int i = 1; i <= n; i++) assert(G[i].size() <= 2);

    for(int i = 1; i <= n; i++) if(G[i].size() == 1) {
        root = i;
        break;
    }
    assert(root != 0);
    predfs(root, -1);
    c1 = k;
    build(1, 1, n);
    for(int i = 1; i <= n; i++) b[a[i]].push_back(i);
    for(int i = 1; i <= k; i++) if(!b[i].empty()) {
        addedge2(1, 1, n, b[i][0], b[i].back(), i);
    }    
    for(int i = 1; i <= c1; i++) if(!num[i]) dfs(i);
    for(int i = 1; i <= c1; i++) {
        for(int j : G2[i]) if(col[i] != col[j]) {
            deg[col[i]] += (val[col[j]] > 0);
        }
    }
    res = n - 1;
    for(int i = 1; i <= ct; i++) if(val[i] > 0) {
        if(!deg[i]) res = min(res, val[i] - 1);
    }
    cout << res;
    // for(int i = 1; i <= k; i++) cout << col[i] << " ";

    // debug
    // for(int i = 1; i <= n; i++) cerr << a[i] << " ";

    return 0 ^ 0;
}

• Subtask 1: 0 / 1
• Subtask 2: 0 / 10
• Subtask 3: 0 / 30
• Subtask 4: 0 / 59