POJ 2513 Colored Sticks

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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?

【题目分析】
这道题还是比较综合的，hash用map太慢，用普通的trie树节点过多，左儿子、右兄弟又太慢。于是遇到了这种带指针的trie，比较简单而且方便。
人生第一份带指针的代码

【代码】

#include <cstdio>#include <cstring>int f[500001],rank[500001],deg[500001],n;struct trie{    int color;    trie *next[26];    trie()    {        color=0;        memset(next,0,sizeof (next));    }}*root;int insert(trie *p,char str[]){    int i;    for (i=0;str[i]!='\0';++i)    {        int s=str[i]-'a';        if (p->next[s]==NULL) p->next[s]=new trie;        p=p->next[s];        if (str[i+1]=='\0')        {            if (p->color==0) p->color=++n;            deg[p->color]++;        }    }    return p->color;}inline void init(){for (int i=1;i<=50000;++i) f[i]=i;}inline int gf(int k){    if (f[k]==k) return k;    else return f[k]=gf(f[k]);}inline void un(int a,int b){    int fa=gf(a),fb=gf(b);    if (fa==fb) return ;    f[fa]=fb;}inline void read(){    char s1[11],s2[11];    int x,y;    n=0,root=new trie;    init();    while (~scanf("%s%s",s1,s2))    {        x=insert(root,s1);        y=insert(root,s2);        un(x,y);    }}inline bool cal(){    int flag=0;    for (int i=1;i<=n;++i)    {        if (flag&&f[i]==i) return false;        if (f[i]==i) flag=1;    }    int x=0;    for (int i=1;i<=n;++i) if (deg[i]%2) x++;    if (x==0||x==2) return true;    return false;}int main(){    read();    if (cal()) printf("Possible\n");    else printf("Impossible\n");}

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