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求樹的重心

#include<iostream>
#include<vector>
#include<cstdio>
#include<cstring>
using namespace std;
typedef long long ll;
const int maxn=200005;
vector<int> tree[maxn];
int n,minNode,minBalance;
//minNode當前重心節點
//minBalance當前重心節點的最大子樹節點個數 
int d[maxn];
//d[i]表示以i為根的子樹節點個數 
void dfs(int u,int
fa){ d[u]=1; //節點本身 int maxSub=0,size=tree[u].size(); //maxSub為節點u的最大子樹節點個數 for(int i=0;i<size;i++){ int v=tree[u][i]; if(v!=fa){ dfs(v,u); d[u]+=d[v]; maxSub=max(maxSub,d[v]); } } maxSub=max(maxSub,n-d[u]); if(maxSub<minBalance){ minNode
=u; minBalance=maxSub; } } int main(){ int t; cin>>t; while(t--){ cin>>n; for(int i=1;i<=n;i++) tree[i].clear(); memset(d,0,sizeof(d)); for(int i=1;i<n;i++){ int u,v; cin>>u>>v; tree[u].push_back(v); tree[v].push_back(u); } minNode
=0; minBalance=0x3f3f3f3f; dfs(1,0); printf("%d %d\n",minNode,minBalance); } return 0; }