Submission #824971

#	Time	Username	Problem	Language	Result	Execution time	Memory
824971		phoenix	Meetings 2 (JOI21_meetings2)	C++17	100 / 100	438 ms	58272 KiB

meetings2

#include<bits/stdc++.h>

using namespace std;
using ll = long long;

const int N = 3e5 + 10;
const int INF = 1e9;
vector<int> g[N];

int n;
int sz[N];
int anc[N][20];
int tin[N], tout[N], T, depth[N];
void precalc(int s, int p) {
    if(s == p) T = 0, depth[s] = 0;
    sz[s] = 1;
    anc[s][0] = p;
    tin[s] = T++;
    for(int i = 1; i < 20; i++) 
        anc[s][i] = anc[anc[s][i - 1]][i - 1];
    for(int to : g[s]) {
        if(to == p) continue;
        depth[to] = depth[s] + 1;
        precalc(to, s);
        sz[s] += sz[to];
    }
    tout[s] = T++;
}
bool up(int u, int v) {
    return tin[u] <= tin[v] && tout[u] >= tout[v];
}
int lca(int u, int v) {
    if(up(u, v)) return u;
    if(up(v, u)) return v;
    for(int i = 19; i >= 0; i--) {
        if(!up(anc[u][i], v)) u = anc[u][i];
    }
    return anc[u][0];
}
int dist(int u, int v) {
    return depth[u] + depth[v] - 2 * depth[lca(u, v)];
}
int root;
vector<int> rs(N, 1);
int LIM;
int func(int u, int v) {
    if(sz[u] < sz[v]) swap(u, v);
    return min(sz[v], n - sz[v]);
}
vector<int> ver[N];
int lb[N];

void DFS(int s, int p) {
    lb[s] = 1;
    for(int to : g[s]) {
        if(to == p) continue;
        DFS(to, s);
        lb[s] = max(lb[to], lb[s]);
    }
    while(lb[s] <= min(sz[s], LIM)) {
        ver[lb[s]++].push_back(s); 
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin >> n;
    vector<pair<int, int>> edges;
    for(int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        edges.push_back({a, b});
        g[a].push_back(b);
        g[b].push_back(a);
    }
    if(n == 1) {
        cout << 1;
        return 0;
    }

    precalc(1, 1);
    int x0 = edges[0].first, x1 = edges[0].second;
    for(auto [u, v] : edges) {
        if(func(x0, x1) < func(u, v)) {
            x0 = u;
            x1 = v;
        }
    }
    LIM = func(x0, x1);
    g[x0].erase(find(g[x0].begin(), g[x0].end(), x1));
    g[x1].erase(find(g[x1].begin(), g[x1].end(), x0));
    root = n + 1;
    g[root].push_back(x0);
    g[root].push_back(x1);

    precalc(root, root);
    DFS(root, root);

    for(int i = 1; i <= LIM; i++) {
        if(ver[i].size() < 2) break;
        int x = ver[i][0], w = 0;
        for(int c : ver[i]) {
            if(depth[c] > depth[x]) x = c;
        }
        for(int c : ver[i]) {
            int v = dist(c, x) + (lca(c, x) != root); 
            w = max(w, v);
        } 
        rs[2 * i] = w;
    }
    for(int i = 1; i <= n; i++) 
        cout << rs[i] << '\n';
}

• Subtask 1: 4 / 4
• Subtask 2: 16 / 16
• Subtask 3: 80 / 80