poj 2513 Colored Sticks

Tire + 并查集 + Eular回路，花了老长时间呢。

#include <stdio.h>
#include <string.h>
const int N = 500050;
int next[5*N][26],d[5*N],cnt=0;
int fa[N],col[N],D[N],color=0;
int inst(char *t)
{
    int u = 0,idx;
    while(*t)
    {
        idx = *t -'a';
        if(!next[u][idx])
        {
            memset(next[cnt++],0,sizeof next[0]);
            next[u][idx] = cnt;
        }
        u = next[u][idx];
        t++;
    }
    if(!d[u])
        color++,col[u] = color,D[color] = u;
    d[u]++;
    return col[u];
}
int find(int a)
{
    int r=a,b=a,t;
    while(fa[r] != r) r = fa[r];
    while(b != r)
    t = b, b = fa[b], fa[t] = r;
    return r;
}
bool divide()
{
    for(int i = 2; i <= color; i++)
        if(find(i) != fa[1]) return 1;
    return 0;
}
bool Eular()
{
    int f=0,i;
    for(i = 1; i <= color; i++)
    {
        if(d[D[i]] & 1) f++;
        if(f >= 3) return 0;
    }
    return 1;
}
int main()
{
    char t[15],s[15];
    int x,y;
    memset(d,0,sizeof(d));
    for(int i = 0; i < N; i++)
        fa[i] = i;
    while(~scanf("%s%s",t,s))
    {
        x = find(inst(t));
        y = find(inst(s));
        fa[y] = x;
    }
    if(divide() || !Eular())
        printf("Impossible\n");
    else printf("Possible\n");
    return 0;
}