bzoj1596[Usaco2008 Jan]电话网络*

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <queue>
 5 #define inc(i,j,k) for(int i=j;i<=k;i++)
 6 #define maxn 10010
 7 using namespace std;
 8 
 9 inline int read(){
10     char ch=getchar(); int f=1,x=0;
11     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1; ch=getchar();}
12     while(ch>=‘0‘&&ch<=‘9‘)x=x*10+ch-‘0‘,ch=getchar();
13     return f*x;
14 }
15 struct e{int t,n;}es[2*maxn]; int ess,g[maxn];
16 void pe(int f,int t){
17     es[++ess]=(e){t,g[f]}; g[f]=ess; es[++ess]=(e){f,g[t]}; g[t]=ess;
18 }
19 int n,ans; bool cov[maxn];
20 void dfs(int x,int fa){
21     bool f=0;
22     for(int i=g[x];i;i=es[i].n)if(es[i].t!=fa){
23         dfs(es[i].t,x); if(cov[es[i].t])f=1;
24     }
25     if(!f&&!cov[x]&&!cov[fa])ans++,cov[fa]=1;
26 }
27 int main(){
28     n=read(); inc(i,1,n-1){int x=read(),y=read(); pe(x,y);} dfs(1,0); printf("%d",ans); return 0;
29 }