Poj 3107 godfather

Http://poj.org/problem? Id = 3107

Tree 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 node15 {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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Poj 3107 godfather