UVa 10054 (打印欧拉回路) The Necklace

将每个颜色看成一个顶点，对于每个珠子在两个颜色之间连一条无向边，然后求欧拉回路。

 #include <cstdio>
 #include <cstring>

 const int maxn =  + ;
 int G[maxn][maxn], deg[maxn];

 void Euler(int u)
 {
     for(int v = ; v <= ; v++) if(G[u][v])
     {
         G[u][v]--; G[v][u]--;
         Euler(v);
         printf("%d %d\n", v, u);
     }
 }

 int main()
 {
     //freopen("in.txt", "r", stdin);

     int T; scanf("%d", &T);
     for(int kase = ; kase <= T; kase++)
     {
         memset(G, , sizeof(G));
         memset(deg, , sizeof(deg));

         if(kase > ) puts("");
         printf("Case #%d\n", kase);

         int n, a, b, st;
         scanf("%d", &n);
         for(int i = ; i < n; i++)
         {
             scanf("%d%d", &a, &b);
             st = a;
             deg[a]++; deg[b]++;
             G[a][b]++; G[b][a]++;
         }

         bool ok = true;
         for(int i = ; i <= ; i++) if(deg[i] % ) { ok = false; break; }
         if(!ok) { puts("some beads may be lost"); continue; }

         Euler(st);

     }

     return ;
 }

代码君