POJ 2513 Colored Sticks

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
int fa[510000],trie[510000][30],dev[510000],id[510000],sz,num;
int getfa(int x)
{
return fa[x] == x ? x : fa[x] = getfa(fa[x]);
}
void init()
{
for(int i = 0; i < 510000; i++)
fa[i] = i;
memset(trie,0,sizeof(trie));
memset(dev,0,sizeof(dev));
memset(id,0,sizeof(id));
sz = 1;
num = 0;
}
int Insert(char *s)
{
int cur = 1;
for(int i = 0; s[i]; i++)
{
int c = s[i] - 'a';
if(!trie[cur][c])
{
trie[cur][c] = ++sz;
}
cur = trie[cur][c];
}
dev[cur]++;
if(dev[cur] == 1) id[cur] = ++num;
return id[cur];
}
int main()
{
char s1[15],s2[15];
init();
while(scanf("%s%s",s1,s2)!=EOF)
{
int a = Insert(s1);
int b = Insert(s2);
//printf("%s %s\n",s1,s2);
int x = getfa(a);
int y = getfa(b);
if(x != y) fa[y] = x;
}
if(num == 0)
{
printf("Possible\n");
return 0;
}
int count1 = 0;
for(int i = 1; i <= sz; i++)
{
if(dev[i]&1) count1 ++;//计算度为奇的点的个数。
if(count1 > 2) break;
}
int count2 = 0;
for(int i = 1; i <= num; i++)
if(fa[i] == i) count2++;//count2 == 1说明联通。
if(count2 == 1 && (count1 == 0 || count1 == 2)) printf("Possible\n");
else printf("Impossible\n");
return 0;
}