poj 2513

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欧拉回路+并查集（判断图的联通）+Tire树（快速查找字符串，并且记录相应点的度数）

Tire树相关知识http://zh.wikipedia.org/wiki/Trie

#include <iostream>using namespace std;const int maxc = 26;const int maxn = 500001;struct TrieNode{int key;TrieNode * child[maxc];TrieNode(){key=-1;memset(child,0,sizeof(child));}};int count[maxn];TrieNode * root;int tot=-1;int insert(char * s){if(root==NULL) root=new TrieNode;int did;TrieNode * tem=root;for(;*s!='\0';s++){did=*s-'a';if(tem->child[did]==NULL)tem->child[did]=new TrieNode;tem=tem->child[did];}if(tem->key==-1)tem->key=++tot;count[tem->key]++;return tem->key;}struct UFSTree{int val;int parent;int rank;}t[maxn];void init(){for(int i=0;i<maxn;i++){t[i].val=i;t[i].parent=i;t[i].rank=0;}}int find(int k){if(t[k].val!=t[k].parent)t[k].parent=find(t[k].parent);return t[k].parent; }void Union(int p1,int p2){if(t[p1].rank>t[p2].rank)t[p2].parent=p1;else{t[p1].parent=p2;if(t[p1].rank==t[p2].rank)t[p2].rank++;}}int main(){char f[11],s[11];init();while(scanf("%s %s",f,s)!=EOF){int k1=insert(f);int k2=insert(s);int p1=find(k1);int p2=find(k2);if(p1!=p2)Union(p1,p2);}if(root==NULL) {cout<<"Possible"<<endl;return 0;}int pa1=find(0);int flag=1,i;for(i=1;i<=tot;i++){if(find(i)!=pa1){flag=0;break;}}if(!flag)cout<<"Impossible"<<endl;else{int dam=0;for(i=0;i<=tot;i++){if(count[i]%2!=0) dam++;}if(dam!=2&&dam!=0)cout<<"Impossible"<<endl;elsecout<<"Possible"<<endl;}return 0;}