Submission #571876

#	Time	Username	Problem	Language	Result	Execution time	Memory
571876		dantoh000	Meetings 2 (JOI21_meetings2)	C++14	100 / 100	339 ms	40592 KiB

meetings2

#include <bits/stdc++.h>
using namespace std;
int n;
vector<int> G[200005];
int sz[200005];
int p[18][200005];
int d[200005];
int ord[200005];
int ans[200005];
bool cmp(int a, int b){
    return sz[a] > sz[b];
}
void dfs(int u){
    sz[u] = 1;
    for (auto v: G[u]){
        if (v == p[0][u]) continue;
        p[0][v] = u;
        d[v] = d[u]+1;
        dfs(v);
        sz[u] += sz[v];
    }
}
int dfs2(int u){
    for (auto v : G[u]){
        if (v == p[0][u]) continue;
        if (sz[v] > n/2) return dfs2(v);
    }
    return u;
}
int lca(int u, int v){
    if (d[u] < d[v]) swap(u,v);
    int diff = d[u]-d[v];
    for (int k = 17; k >= 0; k--){
        if (diff>>k&1) u = p[k][u];
    }
    if (u == v) return u;
    for (int k = 17; k >= 0; k--){
        if (p[k][u] && p[k][v] && p[k][u] != p[k][v]){
            u = p[k][u];
            v = p[k][v];
        }
    }
    assert(p[0][u] == p[0][v]);
    return p[0][u];
}
int dist(int u, int v){
    return d[u] + d[v] - 2*d[lca(u,v)];
}
int main(){
    scanf("%d",&n);
    for (int i = 1,u,v; i < n; i++){
        scanf("%d%d",&u,&v);
        G[u].push_back(v);
        G[v].push_back(u);
    }
    dfs(1);
    int c = dfs2(1);
    for (int i = 1; i <= n; i++){
        p[0][i] = 0;
    }
    d[c] = 0;
    dfs(c);
    for (int k = 1; k < 18; k++){
        for (int i = 1; i <= n; i++){
            p[k][i] = p[k-1][p[k-1][i]];
        }
    }
    iota(ord, ord+n, 1);
    sort(ord, ord+n, cmp);
    int end1 = c, end2 = c;
    int L = 1;
    for (int i = 0; i < n; i++){
        int j = ord[i];
        ///printf("%d %d\n",j,sz[j]);
        int d1 = dist(j, end1) + 1;
        int d2 = dist(j, end2) + 1;
        if (d1 < d2){
            swap(d1,d2);
            swap(end1,end2);
        }
        if (d1 > L){
            L = d1;
            end2 = j;
        }
        ans[sz[j]] = L;
    }
    for (int i = n; i >= 1; i--){
        ans[i] = max(ans[i], ans[i+1]);
    }
    for (int i = 1; i <= n; i++){
        if (i%2 == 1) printf("1\n");
        else printf("%d\n",ans[i/2]);
    }


}

Compilation message (stderr)

meetings2.cpp: In function 'int main()':
meetings2.cpp:50:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
meetings2.cpp:52:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |         scanf("%d%d",&u,&v);
      |         ~~~~~^~~~~~~~~~~~~~

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