Tree Cutting （树形dp+树的重心变形）

After Farmer John realized that Bessie had installed a "tree-shaped" network among his N (1 <= N <= 10,000) barns at an incredible cost, he sued Bessie to mitigate his losses.

Bessie, feeling vindictive, decided to sabotage Farmer John's network by cutting power to one of the barns (thereby disrupting all the connections involving that barn). When Bessie does this, it breaks the network into smaller pieces, each of which retains full connectivity within itself. In order to be as disruptive as possible, Bessie wants to make sure that each of these pieces connects together no more than half the barns on FJ.

Please help Bessie determine all of the barns that would be suitable to disconnect.

Input

* Line 1: A single integer, N. The barns are numbered 1..N.

* Lines 2..N: Each line contains two integers X and Y and represents a connection between barns X and Y.

Output

* Lines 1..?: Each line contains a single integer, the number (from 1..N) of a barn whose removal splits the network into pieces each having at most half the original number of barns. Output the barns in increasing numerical order. If there are no suitable barns, the output should be a single line containing the word "NONE".

Sample Input

101 22 33 44 56 77 88 99 103 8

Sample Output

38

Hint

INPUT DETAILS:

The set of connections in the input describes a "tree": it connects all the barns together and contains no cycles.

OUTPUT DETAILS:

If barn 3 or barn 8 is removed, then the remaining network will have one piece consisting of 5 barns and two pieces containing 2 barns. If any other barn is removed then at least one of the remaining pieces has size at least 6 (which is more than half of the original number of barns, 5).

题目大概：

给你一棵树，找出这样的节点，节点的子树中含有节点树最多的不超过总节点树的一半。

思路：

其实这个节点的限制也可以说是树的重心的定义，但不是最少的结点数，这个我把求树的重心的代码改了一点。

代码：

#include <iostream>#include <cstdio>#include <cstring>#include <vector>using namespace std;int n;int d[50005];int dp[50005];int head[50005];int minshu;int ans;struct shu{    int v;    int next;}tr[100005];void add(int q,int w){    tr[ans].v=w;    tr[ans].next=head[q];    head[q]=ans++;}void dfs(int x,int pa){    d[x]=1;    int maxshu=-1000000;    for(int i=head[x];i!=-1;i=tr[i].next)    {        int son=tr[i].v;        if(son!=pa)        {            dfs(son,x);            d[x]+=d[son];            maxshu=max(maxshu,d[son]);        }    }    dp[x]=max(maxshu,n-d[x]);}int main(){    while(~scanf("%d",&n))    {        memset(dp,0,sizeof(dp));         memset(d,0,sizeof(d));          memset(head,-1,sizeof(head));        ans=0;        for(int i=1;i<n;i++)        {            int q,w;            scanf("%d%d",&q,&w);            add(q,w);            add(w,q);        }    minshu=n/2;    dfs(1,-1);    for(int i=1;i<=n;i++)    {        if(dp[i]<=minshu)        {            printf("%d\n",i);        }    }    }    return 0;}