| Time Limit: 3000MS | 64bit IO Format: %lld & %llu |
1 /*by SilverN*/ 2 #include<iostream> 3 #include<algorithm> 4 #include<cstring> 5 #include<cstdio> 6 #include<cmath> 7 #include<vector> 8 #include<queue> 9 using namespace std; 10 const int mxn=20000; 11 vector<int>e[mxn]; 12 int f[mxn][5]; 13 int vis[mxn]; 14 int n; 15 void dp(int u){ 16 int i,j; 17 vis[u]=1; 18 f[u][0]=1;f[u][1]=0;f[u][2]=mxn; 19 queue<int>q; 20 for(i=0;i<e[u].size();i++){ 21 int v=e[u][i]; 22 if(!vis[v]){ 23 dp(v); 24 q.push(v); 25 f[u][0]+=min(f[v][1],f[v][0]); 26 f[u][1]+=f[v][2]; 27 } 28 } 29 while(!q.empty()){ 30 f[u][2]=min(f[u][2],f[u][1]-f[q.front()][2]+f[q.front()][0]); 31 q.pop(); 32 } 33 return; 34 } 35 int main(){ 36 int i,j; 37 while(scanf("%d",&n) && n!=-1){ 38 if(!n)continue; 39 memset(f,0,sizeof f); 40 memset(vis,0,sizeof vis); 41 for(i=1;i<=n;i++) e[i].clear(); 42 int x,y; 43 for(i=1;i<n;i++){ 44 scanf("%d%d",&x,&y); 45 e[x].push_back(y); 46 e[y].push_back(x); 47 } 48 dp(1); 49 printf("%d ",min(f[1][0],f[1][2])); 50 } 51 return 0; 52 }