poj2513 Colored Sticks 字典树+并查集+欧拉路

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 redred violetcyan blueblue magentamagenta 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;}