【UER #4】被删除的黑白树

 1 #include<bits/stdc++.h>
 2 #define inc(i,l,r) for(i=l;i<=r;i++)
 3 #define dec(i,l,r) for(i=l;i>=r;i--)
 4 #define mem(a) memset(a,0,sizeof(a))
 5 #define inf 1e9
 6 #define ll long long
 7 #define succ(x) (1<<x)
 8 #define NM  100000+5
 9 using namespace std;
10 int read(){
11     int x=0,f=1;char ch=getchar();
12     while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();}
13     while(isdigit(ch))x=x*10+ch-‘0‘,ch=getchar();
14     return x*f;
15 }
16 struct edge{
17     int t;
18     edge *next;
19 }e[2*NM],*h[NM];
20 int n,i,ans,d[NM],s,_x,_y,b[NM];
21 bool v[NM];
22 void add(int x,int y){
23     e[++s].t=y;e[s].next=h[x];h[x]=e+s;
24 }
25 void _dfs(int x){
26     v[x]++;b[x]=inf;
27     for(edge *j=h[x];j;j=j->next)
28     if(!v[j->t]){
29         d[j->t]=d[x]+1;
30         _dfs(j->t);
31         b[x]=min(b[x],b[j->t]);
32     }
33     if(b[x]==inf)b[x]=0;
34     b[x]++;
35 }
36 void dfs(int x,int k){
37     v[x]++;d[x]=0;
38     for(edge *j=h[x];j;j=j->next)
39     if(!v[j->t]){
40         dfs(j->t,min(b[x]-1,k));
41         d[x]+=d[j->t];
42     }
43     if(b[x]==k)d[x]++;
44 }
45 int main(){
46 //    freopen("test.in","r",stdin);
47     n=read();
48     inc(i,1,n-1){
49         _x=read();_y=read();
50         add(_x,_y);add(_y,_x);
51     }
52     d[1]++;
53     _dfs(1);
54     mem(v);
55     dfs(1,b[1]);
56     printf("%d\n",d[1]);
57     return 0;
58 }