pku 2513 Colored Sticks 欧拉通路问题

#include <iostream>
using namespace std;
#define swap(i,j) {int temp=i; i = j; j = temp;}
struct Node
{
int index;
Node* arr[26];
Node()
{
index = -1;
memset(arr, 0, sizeof(arr));
}
};
int parent[500001];
int degree[500001];

Node* root = new Node(); //根节点
int words_count = 0; //不同的单词的总的个数

int get_num(char* str)
{
Node* p = root;
while(*str)
{
int index = *str-'a';
if(!p->arr[index])
p->arr[index] = new Node();
p = p->arr[index];
str++;
}
if(p->index == -1)
p->index = words_count++;
return p->index;
}

int ufset_find(int i)
{
int p = i;
while(parent[p] >= 0)
p = parent[p];
while(i != p)
{
parent[i] = p;
i = parent[i];
}
return p;
}

void ufset_union(int i, int j)
{
i = ufset_find(i);
j = ufset_find(j);
if(i == j)
return;

if(parent[i] < parent[j])
swap(i, j);

parent[i] += parent[j]; //注意这两行的先后顺序!
parent[j] = i;
}

int main()
{
memset(parent, -1, sizeof(parent));
memset(degree, 0, sizeof(degree));
char str1[11], str2[11];
while(scanf("%s %s", str1, str2) != EOF)
{
int i = get_num(str1);
int j = get_num(str2);
degree[i]++;
degree[j]++;
ufset_union(i, j);
}

if(!words_count)
{
printf("Possible/n");
return 0;
}

if(parent[ufset_find(0)] + words_count)
{
printf("Impossible/n");
return 0;
}

int cnt = 0;
for(int i = 0; i < words_count; ++i)
if(degree[i]&1)
cnt++;
if(cnt == 2 || cnt == 0)
printf("Possible/n");
else
printf("Impossible/n");
return 0;
}