poj 2513 Colored Sticks (无向欧拉路+字典树）

You are given a bunch of wooden sticks. Each endpoint of each stick is colored with some color. Is it possible to align the sticks in a straight line such that the colors of the endpoints that touch are of the same color?

Input
Input is a sequence of lines, each line contains two words, separated by spaces, giving the colors of the endpoints of one stick. A word is a sequence of lowercase letters no longer than 10 characters. There is no more than 250000
sticks.

Output
If the sticks can be aligned in the desired way, output a single line saying Possible, otherwise output Impossible.

Sample Input

blue red
red violet
cyan blue
blue magenta
magenta cyan

Sample Output

Possible

Hint
Huge input,scanf is recommended.

给出m对数 判断是否构成欧拉路（所有边当且仅遍历一遍），当奇数度数大于2时不成立；成立条件：一条直线，或者环，或者直线加环；

有向为（有一个入度-出度=1，出度-入度=1）；

用map（内部排序）标记超时，poj不支持unordered_map,所以用字典树优化

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>
#include <map>
#include <queue>
#include <string>
using namespace std;
const int N = 500000+5;
char s1[30], s2[30];
int degree
, f
;
struct node
{
int id;
node *next2[30];
node(){
id=0;
for(int i=0;i<26;i++)
next2[i]=NULL;
}
};
node *root;
int k;
int getid(char *s)
{
int len=strlen(s);
node *p=root;
node *tmp=NULL;
for(int i=0;i<len;i++)
{
if(!p->next2[s[i]-'a'])
{
tmp=new node;
p->next2[s[i]-'a']=tmp;
}
p=p->next2[s[i]-'a'];
}
if(p->id==0) p->id=++k;
return p->id;
}
int getf(int x)
{
if(x!=f[x]) f[x]=getf(f[x]);
return f[x];
}

void unio(int x,int y)
{
int t1=getf(x), t2=getf(y);
if(t1!=t2) f[t1]=t2;
return ;
}

int main()
{
k=0;
root=new node;
for(int i=0; i<N; i++) f[i]=i;
while(scanf("%s %s", s1, s2)!=EOF)
{
int id1=getid(s1), id2=getid(s2);
degree[id1]++,degree[id2]++;
unio(id1,id2);
}
int s=getf(1),num=0;
for(int i=1; i<k; i++)
{
if(num>2)
{
puts("Impossible");
return 0;
}
if(getf(i)!=s)
{
puts("Impossible");
return 0;
}
if(degree[i]%2==1) num++;
}
if(num>2) puts("Impossible");
else puts("Possible");
return 0;
}