poj 3107 Godfather

http://poj.org/problem?id=3107

树形dp

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #define maxn 55000
 5 using namespace std;
 6 const int inf=1<<30;
 7 
 8 int head[maxn],e,n;
 9 int dp[maxn];
10 bool vis[maxn];
11 int minn;
12 int cnt;
13 int ans[maxn];
14 struct node
15 {
16     int u,v;
17     int next;
18 }p[maxn*2];
19 
20 void add(int u,int v)
21 {
22     p[e].u=u;
23     p[e].v=v;
24     p[e].next=head[u];
25     head[u]=e++;
26 }
27 
28 void cls()
29 {
30    e=0;
31    cnt=0;
32    memset(ans,0,sizeof(ans));
33    minn=inf;
34    memset(head,-1,sizeof(head));
35 }
36 
37 void dfs(int u)
38 {
39     int min1=-1;
40     if(vis[u]) return ;
41     vis[u]=true;
42     dp[u]=1;
43     for(int i=head[u]; i!=-1; i=p[i].next)
44     {
45         int v=p[i].v;
46         if(vis[v]) continue;
47         dfs(v);
48         dp[u]+=dp[v];
49         min1=max(min1,dp[v]);
50     }
51     min1=max(min1,n-dp[u]);
52     if(min1<minn)
53     {
54         cnt=0;
55         ans[cnt++]=u;
56         minn=min1;
57     }
58     else if(min1==minn)
59     {
60         ans[cnt++]=u;
61     }
62 }
63 
64 int main()
65 {
66     while(scanf("%d",&n)!=EOF)
67     {
68         cls();
69         for(int i=1; i<=n-1; i++)
70         {
71             int u,v;
72             scanf("%d%d",&u,&v);
73             add(u,v);
74             add(v,u);
75         }
76         dfs(1);
77         sort(ans,ans+cnt);
78         for(int i=0; i<cnt; i++)
79         {
80             if(i==0) printf("%d",ans[i]);
81             else printf(" %d",ans[i]);
82         }
83         printf("\n");
84     }
85     return 0;
86 }
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posted @ 2014-09-27 19:08  null1019  阅读(105)  评论(0编辑  收藏  举报