POJ 1947 Rebuilding Roads

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <vector>
 5 using namespace std;
 6 const int maxn = 200;
 7 int n,k,ret,dp[maxn][maxn],son[maxn];
 8 vector<int>g[maxn];
 9 int dfs(int u){
10     son[u] = 1;
11     for(int i = g[u].size()-1; i >= 0; --i) son[u] += dfs(g[u][i]);
12     dp[u][1] = g[u].size();//u有g[u].size()个直系儿子 删除儿子还剩自己
13     for(int i = g[u].size()-1; i >= 0; --i){
14         for(int j = son[u]; j > 0; --j)
15             for(int k = 1; k < j && k <= son[g[u][i]]; ++k)
16                 dp[u][j] = min(dp[u][j],dp[u][j - k] + dp[g[u][i]][k] - 1);
17     }
18     if(son[u] >= k) ret = min(ret,dp[u][k] + (u != 1));
19     return son[u];
20 }
21 int main(){
22     int u,v;
23     while(~scanf("%d%d",&n,&k)){
24         for(int i = 0; i < maxn; ++i) g[i].clear();
25         for(int i = 1; i < n; ++i){
26             scanf("%d%d",&u,&v);
27             g[u].push_back(v);
28         }
29         memset(dp,0x3f,sizeof dp);
30         memset(&ret,0x3f,sizeof ret);
31         dfs(1);
32         printf("%d\n",ret);
33     }
34     return 0;
35 }