Codeforces 219D Choosing Capital for Treeland

 1 // File Name: 219d.cpp
 2 // Author: darkdream
 3 // Created Time: 2015年03月10日 星期二 19时26分38秒
 4 
 5 #include<vector>
 6 #include<list>
 7 #include<map>
 8 #include<set>
 9 #include<deque>
10 #include<stack>
11 #include<bitset>
12 #include<algorithm>
13 #include<functional>
14 #include<numeric>
15 #include<utility>
16 #include<sstream>
17 #include<iostream>
18 #include<iomanip>
19 #include<cstdio>
20 #include<cmath>
21 #include<cstdlib>
22 #include<cstring>
23 #include<ctime>
24 #define LL long long
25 #define maxn 200006
26 using namespace std;
27 map <int,int> mp[maxn];
28 vector<int>  dmp[maxn]; 
29 int n ;
30 int dpx[maxn];
31 int dfs(int k ,int la )
32 {
33    for(int i = 0 ;i < dmp[k].size();i ++)
34    {
35         if(dmp[k][i] == la)
36              continue;
37         if(mp[k][dmp[k][i]] == 0)
38             dpx[k] ++ ;
39         dpx[k] += dfs(dmp[k][i],k);
40    }
41    return dpx[k];
42 
43 }
44 void dfs2(int k ,int s,int la)
45 {
46    dpx[k] += s; 
47    for(int i = 0 ;i < dmp[k].size() ;i ++)
48     {
49          if(dmp[k][i] == la)
50              continue;
51          int tmp = dpx[k] - dpx[dmp[k][i]];
52          if(mp[k][dmp[k][i]] == 1)
53              tmp ++ ;
54          else tmp -- ;
55          dfs2(dmp[k][i],tmp,k) ;
56     }
57 }
58 int main(){
59      scanf("%d",&n);
60      memset(dpx,0,sizeof(dpx));
61      for(int i = 1 ;i < n;i ++)
62      {
63          int ta, tb; 
64          scanf("%d %d",&ta,&tb);
65          dmp[ta].push_back(tb);
66          dmp[tb].push_back(ta);
67          mp[ta][tb] = 1; 
68      }
69      dfs(1,0);
70      dfs2(1,0,0);
71      int mi = 1e9 ; 
72      for(int i = 1;i <= n;i ++)
73      {
74         mi = min(mi,dpx[i]);
75         //printf("%d ",dpx[i]);
76      }
77      printf("%d\n",mi);
78      for(int i = 1;i <= n;i ++)
79          if(dpx[i] == mi)
80              printf("%d ",i);
81 return 0;
82 }