Description
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
就是让你把这几根棒子排在一起看能不能成环，先存着，下次来写
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
struct trie{
bool flag;
int id;
trie* next[27];
};
int color=0,du[500001]={0},f[500001];
int find(int x)
{
if(f[x]!=x)f[x]=find(f[x]);
return f[x];
}
void union1(int a,int b)
{
f[find(b)]=find(a);
}
trie* built()
{
trie* leaf=new trie;
leaf->flag=false;
leaf->id=0;
memset(leaf->next,0,sizeof(leaf->next));
return leaf;
}
int build(trie *&root,char* s)
{
trie* p=root;
int len=0;
while(s[len]!='\0')
{
int x=s[len++]-'a';
if(!p->next[x])p->next[x]=built();
p=p->next[x];
}
if(p->flag)return p->id;
else{
p->flag=true;
p->id=++color;
return p->id;
}
}
int main()
{
trie* root=built();
for(int k=1;k<=500000;k++)f[k]=k;
char a[20],b[20];
while(cin>>a>>b)
{
int i=build(root,a),j=build(root,b);
du[i]++,du[j]++;
union1(i,j);
}
int num=0,s=find(1);
for(int i=1;i<=color;i++)
{
if(du[i]%2==1)num++;
if(num>2||find(i)!=s)
{
cout<<"Impossible\n";
return 0;
}
}
if(num==1)cout<<"Impossible\n";
else cout<<"Possible\n";
return 0;
}