【POJ】2513 Colored Sticks

字典树+并查集。

 #include <cstdio>
 #include <cstring>
 #include <cstdlib>

 #define MAXN  500005
 #define MAXL  11
 #define TRIEN 26

 typedef struct Trie {
     int v;
     Trie *next[TRIEN];
     Trie() {
         v = ;
         for (int i=; i<TRIEN; ++i)
             next[i] = NULL;
     }
 } Trie;

 Trie root;
 int pre[MAXN], deg[MAXN], n = ;

 void create(char str[], int in) {
     int i = , id;
     Trie *p = &root, *q;

     while (str[i]) {
         id = str[i] - 'a';
         ++i;
         if (p->next[id] == NULL) {
             q = new Trie();
             p->next[id] = q;
         }
         p = p->next[id];
     }
     p->v = in;
 }

 int Tfind(char str[]) {
     int i = , id;
     Trie *p = &root;

     while (str[i]) {
         id = str[i] - 'a';
         ++i;
         if (p->next[id] == NULL)
             return ;
         p = p->next[id];
     }

     return p->v;
 }

 int find(int x) {
     return x==pre[x] ? x:pre[x]=find(pre[x]);
 }

 void merge(int a, int b) {
     a = find(a);
     b = find(b);
     if (a != b)
         pre[b] = a;
 }

 bool judge() {
     int cnt = , i;
     if (n == )
         return true;
     for (i=; i<n; ++i) {
         if (pre[i] == i)
             ++cnt;
         if (cnt > )
             return false;
     }
     if (!cnt)
         return false;
     cnt = ;
     for (i=; i<n; ++i)
         if (deg[i] & )
             ++cnt;
     if (cnt== || cnt==)
         return true;
     else
         return false;
 }

 int main() {
     char a[MAXL], b[MAXL];
     int i, k;

     memset(deg, , sizeof(deg));
     for (i=; i<MAXN; ++i)
         pre[i] = i;

     while (scanf("%s %s", a, b) != EOF) {
         k = Tfind(a);
         if (k)
             deg[k]++;
         else {
             create(a, n);
             k = n;
             deg[n++] = ;
         }
         i = Tfind(b);
         if (i)
             deg[i]++;
         else {
             create(b, n);
             i = n;
             deg[n++] = ;
         }
         merge(k, i);
     }

     if (judge())
         printf("Possible\n");
     else
         printf("Impossible\n");

     return ;
 }