Submission #907524

#	Time	Username	Problem	Language	Result	Execution time	Memory
907524		box	Meetings 2 (JOI21_meetings2)	C++17	100 / 100	348 ms	47696 KiB

meetings2

#include <bits/stdc++.h>
using namespace std;

#ifndef LOCAL
#define cerr if (0) cerr
#endif

typedef vector<int> vi;

const int MAXN = 2e5, MAXL = 18;

int N, sz[MAXN];
vi adj[MAXN], who[MAXN+1];
int depth[MAXN], jmp[MAXN][MAXL];
int ans[MAXN+1];

void make_sz(int p, int i) {
    sz[i] = 1;
    for (int j : adj[i]) if (p != j) {
        make_sz(i, j);
        sz[i] += sz[j];
    }
}

void dfs(int i) {
    for (int l = 1; l < MAXL; l++) jmp[i][l] = jmp[jmp[i][l-1]][l-1];
    sz[i] = 1;
    for (int j : adj[i]) if (jmp[i][0]^j) {
        jmp[j][0] = i;
        depth[j] = depth[i]+1;
        dfs(j);
        sz[i] += sz[j];
    }
    who[sz[i]].push_back(i);
}

int lca(int i, int j) {
    if (depth[i] < depth[j]) swap(i, j);
    int d = depth[i]-depth[j];
    for (int l = 0; l < MAXL; l++) if (d>>l&1) i = jmp[i][l];
    if (i == j) return i;
    for (int l = MAXL-1; l >= 0; l--) if (jmp[i][l]^jmp[j][l]) i = jmp[i][l], j = jmp[j][l];
    return jmp[i][0];
}

int dist(int i, int j) {
    return depth[i]+depth[j]-2*depth[lca(i, j)];
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> N;
    for (int i = 0; i < N-1; i++) {
        int x, y; cin >> x >> y, x--, y--;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    int c = [&]() {
        make_sz(-1, 0);
        int i = 0;
        while (1) {
            int c = -1;
            for (int j : adj[i]) if (sz[j] < sz[i] && sz[j]*2 > N) c = j;
            if (c == -1) break;
            i = c;
        }
        return i;
    }();
    cerr << "GOT c=" << c+1 << endl;
    jmp[c][0] = c;
    dfs(c);
    int d = 0, x = c, y = c;
    for (int s = N/2; s >= 1; s--) {
        for (int i : who[s]) {
            int a = dist(x, i), b = dist(y, i);
            if (a < b) swap(a, b), swap(x, y);
            if (a > d) d = a, y = i;
        }
        ans[s*2] = d;
    }
    for (int k = 1; k <= N; k++) cout << ans[k]+1 << '\n';
}

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