POJ 2513 Colored Sticks （欧拉回路 + 字典树 +并查集）

Colored Sticks Time Limit: 5000MS   Memory Limit: 128000K Total Submissions: 27097   Accepted: 7175 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 Hint Huge input,scanf is recommended. Source The UofA Local 2000.10.14

 

详细解释：http://blog.csdn.net/lyy289065406/article/details/6647445

 

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>

using namespace std;

struct Trie{
    int x;
    Trie *next[26];
}*root,memory[5100000];

int deg[5100000],father[510000],cnt,tot;

Trie *create(){
    Trie *p=&memory[cnt++];
    for(int i=0;i<26;i++)
        p->next[i]=NULL;
    return p;
}

void InsertTrie(char *str,int x){
    Trie *loc=root;
    for(int i=0;str[i]!='\0';i++){
        int id=str[i]-'a';
        if(loc->next[id]==NULL)
            loc->next[id]=create();
        loc=loc->next[id];
    }
    loc->x=x;
}

int SearchTrie(char *str){
    Trie *loc=root;
    for(int i=0;str[i]!='\0';i++){
        int id=str[i]-'a';
        if(loc->next[id]==NULL)
            return 0;
        loc=loc->next[id];
    }
    return loc->x;
}

void init(){
    for(int i=1;i<=501000;i++)
        father[i]=i;
    memset(deg,0,sizeof(deg));
    cnt=0;
    tot=0;
}

int findSet(int x){
    if(x!=father[x]){
        father[x]=findSet(father[x]);
    }
    return father[x];
}

int judge(){        //判断是否满足欧拉 
    int odd=0;
    for(int i=1;i<=tot;i++)
        if(deg[i]%2==1)
            odd++;
    if(odd!=0 && odd!=2)
        return 0;
    int k=findSet(1);
    for(int i=2;i<=tot;i++)
        if(k!=findSet(i))
            return 0;
    return 1;
}

int main(){

    //freopen("input.txt","r",stdin);

    char s1[15],s2[15];
    init();
    root=create();
    while(~scanf("%s%s",s1,s2)){
        int x=SearchTrie(s1);   //映射求编号速度太慢
        int y=SearchTrie(s2);   //用字典树来求编号
        if(x==0)
            InsertTrie(s1,x=++tot);
        if(y==0)
            InsertTrie(s2,y=++tot);
        deg[x]++;
        deg[y]++;
        int fx=findSet(x);
        int fy=findSet(y);
        if(fx!=fy)
            father[fx]=fy;
    }
    if(judge())
        printf("Possible\n");
    else
        printf("Impossible\n");
    return 0;
}