http://codeforces.com/contest/1131/problem/F
题意:有n只猫相邻有隔板隔着,n-1对(x,y)输入表示取下某一隔板能使x与y猫在一起,取下后两笼合并,里面的猫都与相邻笼的猫相邻,输出一组序列,能符合顺序地使得猫在一起;
思路:并查集;连接每个点集合;
#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<ctime>
#include<map>
#include<stack>
#include<string>
using namespace std;
#define sfi(i) scanf("%d",&i)
#define pri(i) printf("%d\n",i)
#define sff(i) scanf("%lf",&i)
#define ll long long
#define mem(x,y) memset(x,y,sizeof(x))
#define INF 0x3f3f3f3f
#define eps 1e-6
#define PI acos(-1)
#define lowbit(x) ((x)&(-x))
#define zero(x) (((x)>0?(x):-(x))<eps)
#define fl() printf("flag\n")
ll gcd(ll a,ll b){while(b^=a^=b^=a%=b);return a;}
const int maxn=3e5+9;
const int mod=1e9+7;
template <class T>
inline void sc(T &ret)
{
char c;
ret = 0;
while ((c = getchar()) < '0' || c > '9');
while (c >= '0' && c <= '9')
{
ret = ret * 10 + (c - '0'), c = getchar();
}
}
vector<int>g[maxn];
int p[maxn];
void dfs(int u,int fa)
{
cout<<u<<" ";
for(int i=0;i<g[u].size();i++)
{
int v=g[u][i];
if(v!=fa)
{
dfs(v,u);
}
}
}
int Find(int x)
{
return p[x]==x?x:p[x]=Find(p[x]);
}
void join(int x,int y)
{
int jx=Find(x);
int jy=Find(y);
if(g[jx].size()<g[jy].size()) swap(jx,jy);
//cout<<jx<<" "<<jy<<endl;
if(jx!=jy)
{
for(int i=0;i<g[jy].size();i++)
{
g[jx].push_back(g[jy][i]);
p[g[jy][i]]=jx;
}
}
}
int main()
{
int n;
cin>>n;
for(int i=1;i<=n;i++) p[i]=i,g[i].push_back(i);
for(int i=0;i<n-1;i++)
{
int u,v;
cin>>u>>v;
join(u,v);
}
for(int i=1;i<=n;i++)
{
if(p[i]==i)
{
for(int j=0;j<g[i].size();j++)
{
cout<<g[i][j]<<" ";
}
break;
}
}
return 0;
}