*rebuilding roads<pku 1947>

 
 1 #include <iostream> 
 2 #include <cstdio> 
 3 #include <cstring> 
 4 #include <vector> 
 5 using namespace std;
 6 #define inf 10000000 
 7 int s[160],p[160],v[160],dp[160][160],n,m;
 8 void check(int root)
 9 {
10     for(int i=0;i<=m;i++) dp[root][i] = inf;
11     dp[root][1]=0;
12     int tem = s[root];
13     while(tem){
14         check(tem);
15         for(int i=m;i>=0;--i){
16             int temm = dp[root][i]+1;
17             for(int j=0;j<=i;++j){
18                 temm = min(temm,dp[tem][i-j]+dp[root][j]);
19             }
20             dp[root][i] = temm;
21         }
22         tem = p[tem];
23     }
24 }
25 int solve(int root)
26 {
27     check(root);
28     int ans = dp[root][m];
29     for(int i=1;i<=n;i++){
30         ans = min(ans,dp[i][m]+1);
31     }
32     return ans;
33 }
34 int main()
35 {
36     int a,b,root;
37     cin>> n>> m;
38     memset(s,0,sizeof(s));
39     memset(v,0,sizeof(v));
40     for(int i=0;i<n-1;i++)
41     {
42         cin>> a>> b;
43         p[b]=s[a];
44         s[a]=b;
45         v[b]=1;
46     }
47     for(int i=1;i<=n;i++) if(!v[i]) root=i;
48     cout<< solve(root)<< endl;
49     return 0;
50 }