POJ 2513 Colored Sticks（欧拉道路+字典树+并查集）

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<string>
 4 #include<cstring>
 5 using namespace std;
 6 
 7 const int maxn = 500000 + 5;
 8 int p[maxn], deg[maxn];
 9 int cnt;
10 
11 struct Trie
12 {
13     int ch[maxn][30];
14     int vis[maxn];
15     int sz;
16 
17     void init()
18     {
19         sz = 1;
20         memset(ch[0], 0, sizeof(ch[0]));
21     }
22 
23     int insert(char *s, int& v)
24     {
25         int u = 0, n = strlen(s);
26         for (int i = 0; i < n; i++)
27         {
28             int c = s[i]-‘a‘;
29             if (!ch[u][c])
30             {
31                 memset(ch[sz], 0, sizeof(ch[sz]));
32                 vis[sz] = 0;
33                 ch[u][c] = sz++;
34             }
35             u = ch[u][c];
36         }
37         if (!vis[u])   vis[u] = ++v;
38         return vis[u];
39     }
40 }t;
41 
42 int find(int x)
43 {
44     return x == p[x] ? x : find(p[x]);
45 }
46 
47 void merge(int x, int y)
48 {
49     int fx = find(x);
50     int fy = find(y);
51     if (fx != fy)
52         p[fx] = fy;
53 }
54 
55 int main()
56 {
57     //freopen("D:\\txt.txt", "r", stdin);
58     char a[20], b[20];
59     t.init();
60     memset(deg, 0, sizeof(deg));
61     for (int i = 0; i <= maxn; i++)   p[i] = i;
62     cnt = 0;
63     while (~scanf("%s %s", a, b))
64     {
65         int id1 = t.insert(a,cnt);
66         int id2 = t.insert(b,cnt);
67         deg[id1]++;
68         deg[id2]++;
69         merge(id1, id2);
70     }
71     int ans = 0;
72     for (int i = 1; i <= cnt; i++)
73     {
74         if (deg[i] % 2 == 1)   ans++;
75         if (ans > 2 || find(1) != find(i))
76         {
77             printf("Impossible\n");
78             return 0;
79         }
80     }
81     if (ans == 1)
82         printf("Impossible\n");
83     else
84         printf("Possible\n");
85     return 0;
86 }