POJ 2513 Colored Sticks <trie+并查集+欧拉路径>

题目：传送门。

分析：我好懒，直接分享一篇题解吧，传送门。

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
using namespace std;

const int MAXN=25e4+5;
class trieTree{
public:
	int id;
	trieTree *next[27];
	trieTree(){
		id=-1;
		memset(next,0,sizeof next);
	}
};
trieTree root;
int degree[MAXN*2];
int ancestor[MAXN*2];
int color;

int getID(char *str){
	trieTree *t=&root;
	for(int i=0;str[i]!='\0';++i){
		int index=str[i]-'a';
		if(!t->next[index]){
			trieTree *tt=new trieTree;
			t->next[index]=tt;
		}
		t=t->next[index];
	}
	return t->id>=0 ? t->id:t->id=color++; 
}

int find(int x){
	if(ancestor[x]!=x){
		ancestor[x]=find(ancestor[x]);
	}
	return ancestor[x];
}

void unionSet(int x,int y){
	int px=find(x),py=find(y);
	ancestor[py]=px;
}

int main(){
	color=0;
	memset(degree,0,sizeof degree);
	for(int i=0;i<MAXN*2;++i) ancestor[i]=i;
	char c1[12],c2[12];
	while(cin>>c1>>c2){
		int x=getID(c1),y=getID(c2);
		unionSet(x,y);
		degree[x]++; degree[y]++;
	}
	int r=find(1),sum=0;
	for(int i=0;i<color;++i){
		if(degree[i]&1) sum++;
		if(find(i)!=r){
			cout<<"Impossible\n";
			return 0;
		}
		if(sum>2){
			cout<<"Impossible\n";
			return 0;
		}
	}
	if(sum==1) cout<<"Impossible\n";
	else cout<<"Possible\n";
	return 0;
}