CF 1042F Leaf Sets

 1 #include<vector>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 int n,m,cnt,tot,rt;
 7 int fa[1000005];
 8 int head[1000005];
 9 int dgr[1000005];
10 struct Edge{
11     int fr;
12     int to;
13     int nxt;
14 }edge[2000005];
15 void addedge(int f,int t){
16     cnt++;
17     edge[cnt].fr=f;
18     edge[cnt].to=t;
19     edge[cnt].nxt=head[f];
20     head[f]=cnt;
21 }
22 int dfs(int u){
23     if(dgr[u]==1)return 1;
24     vector<int>tr;
25     for(int i=head[u];i;i=edge[i].nxt){
26         int v=edge[i].to;
27         if(v==fa[u])continue;
28         fa[v]=u;
29         int tmp=dfs(v);
30         tr.push_back(tmp);
31     }
32     int siz=tr.size();int i;
33     sort(tr.begin(),tr.end());
34     for(i=siz-1;i>=1;i--){
35         if(tr[i]+tr[i-1]<=m)break;
36         tot++;
37     }
38     return tr[i]+1;
39 }
40 int main(){
41     scanf("%d%d",&n,&m);
42     for(int i=1;i<n;i++){
43         int u,v;
44         scanf("%d%d",&u,&v);
45         addedge(u,v);
46         addedge(v,u);
47         dgr[u]++,dgr[v]++;
48         if(dgr[u]>1)rt=u;
49         if(dgr[v]>1)rt=v;
50     }
51     dfs(rt);
52     printf("%d\n",tot+1);
53     return 0;
54 }