樹的重心模板

標籤（空格分隔）： 模板

POJ - 3107

數的重心裸題

#include <cstdio>
#include <vector>
#include <iostream>
using namespace std;

typedef pair<int, int> Pii;
const int MAXN = 5e4 + 50;

int size[MAXN], f[MAXN], n, ans = 0x4f4f4f4f, cnt = 0;
int head[MAXN];
Pii e[MAXN << 1];

inline int read()
{
	int res = 0;
	char ch = getchar();
	
	while(48 > ch || ch > 57)
		ch = getchar();
	while(48 <= ch && ch <= 57){
		res = (res << 3) + (res << 1) + ch - 48;
		ch = getchar();
	}
	
	return res;
}

void add_edge(int u, int v)
{
	e[cnt].first = v;
	e[cnt].second = head[u];
	head[u] = cnt;
	
	cnt ++;
	
	e[cnt].first = u;
	e[cnt].second = head[v];
	head[v] = cnt;
	
	cnt ++;
	
	return;
}

void dfs(int now, int fa)
{
	size[now] = 1;
	int _max = -1;
	for(int i = head[now]; i != -1; i = e[i].second){
		int v = e[i].first;
		if(v == fa)	continue;
		
		dfs(v, now);
		size[now] += size[v];
		_max = max(_max, size[v]);
	}
	f[now] = max(_max, n - size[now]);
	ans = min(ans, f[now]);
	return;
}
int main()
{
	n = read();
	
	for(int i = 0; i <= n; i ++)
		head[i] = -1;
	for(int i = 0; i < n - 1; i ++){
		add_edge(read(), read());
	}
	
	dfs(1, 0);
//	cout << ans; 
	for(int i = 1; i <= n; i ++)
		if(ans == f[i])
			printf("%d ", i);
	return 0;
}