poj 2513 Colored Sticks

http://poj.org/problem?id=2513

题意：有一些棒子，每一根的两头都有两个颜色，将这些棒子相连并且被两根棒子接头处是相同的颜色，求一些这样的棒子是否都可以全部连起来；

思路：首先用tree树给每一种颜色编号，然后用并查集+欧拉路（只有两个或零个奇数结点）；

代码：

View Code

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;
int f[500010] = {0};
int n = 0;
int nn[500010]  ={0};
struct node
{
    int num;
    node *next[27];
};
node *head = NULL;
node *temp = NULL;
node * get()
{
    temp = new node;
    for(int i = 0;i < 27; ++i)
    temp->next[i] = NULL;
    temp->num = 0;
    return temp;
}
void init()
{
    head = get();
    for(int i = 0;i < 500010; ++i)
    {
        f[i] = i;
        nn[i] = 0;
    }
    n = 0;
}
char a[15] = {0};
char b[15]  ={0};
int x = 0;
int y = 0;

int qq(char *s)
{
    node *temp1 = head;
    int q = 0;
    for(int i = 0; s[i]; ++i)
    {
          q = s[i] - 'a';
          if(temp1->next[q] == NULL)
          temp1->next[q] = get();
          temp1 = temp1->next[q];
    }
    if(temp1->num != 0)
        return temp1->num;
    else
    {
        ++n;
        temp1->num = n;
        return n;
    }
}
int find(int x)
{
    if(x != f[x])
    f[x] = find(f[x]);
    return f[x];
}
void unio(int a,int b)
{
    int x = find(a);
    int y = find(b);
    if(x != y)
    f[x] = y;
}
bool check()
{
    int num = 0;
    int tt = find(1);
    for(int i = 1;i <= n; ++i)
    {
       if(find(i) != tt)
       return 0;
       if(nn[i]%2)
       ++num;
    }
    if(num == 0 || num == 2)
    return 1;
    return 0;
}
int main()
{
    //freopen("input.txt","r",stdin);
    init();
    while(scanf("%s%s",a,b) != EOF)
    {
        x = qq(a);
        ++nn[x];
        y = qq(b);
        ++nn[y];
        unio(x,y);
    }
    if(check())
        printf("Possible\n");
     else
     printf("Impossible\n");
     return 0;
}