poj 2513（字典树，并查集，压缩路径）

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 250005;
char data[maxn][2][15];
int number = 0;
int degree[maxn],num,ancestor[maxn];
struct Trie{
    bool exist;
    int count;
    Trie*next[26];
    Trie(){
        exist = false;
        count = 0;
        memset(next,0,sizeof(next));
    }
}root;
int find_ancestor(int x){
    if(ancestor[x]!=x)
        ancestor[x] = find_ancestor(ancestor[x]);
    return ancestor[x];
}
void union_set(int x,int y){
    int px = find_ancestor(x);
    int py = find_ancestor(y);
    ancestor[px] = py;
}
int char2int(char*c){
    int i,len=strlen(c);
    Trie*p = &root;
    for(i=0;i<len;i++){
        if(p->next[c[i]-'a']==NULL){
            p->next[c[i]-'a'] = new Trie;
        }
        p = p->next[c[i]-'a'];
    }
    if(p->exist==false){
        p->exist = true;
        p->count = ++number;
    }
    return p->count;
}
int main(){
    int i,kase = 1;
    bool flag;
    memset(degree,0,sizeof(degree));
    for(i=1;i<maxn;i++){
        ancestor[i] = i;
    }
    while(scanf("%s%s",data[kase][0],data[kase][1])==2){
        int a = char2int(data[kase][0]);
        int b = char2int(data[kase][1]);
        degree[a]++;
        degree[b]++;
        union_set(a,b);
        kase++;
    }
    int s = find_ancestor(1);
    num = 0;
    flag = true;
    for(i=1;i<=number;i++){
        if(degree[i]%2!=0)num++;
        if(num>2){
            flag = false;
            break;
        }
        if(find_ancestor(i)!=s){
            flag = false;
            break;
        }
    }
    if(flag&&num!=1)
        printf("Possible\n");
    else
        printf("Impossible\n");
    return 0;
}