hdu3926 Hand in Hand 同构图

 #include<cstring>
 #include<cstdio>
 #include<algorithm>
 using namespace std;

 int pre[];
 struct e{
     int a, b;
 };
 e s1[];
 e s2[];

 int find(int x)
 {
     while (x != pre[x])
         x = pre[x];
     return x;
 }

 int cmp(e a, e b){
     if (a.a == b.a) return a.b>b.b;
     else return a.a>b.a;
 }

 void init(int n)
 {
     for (int i = ; i <= n; i++)
         pre[i] = i;
 }

 int main()
 {
     int t, cas = ;;
     scanf("%d", &t);
     while (t--)
     {
         for (int i = ; i<; i++)
         {
             s1[i].a = ; s1[i].b = ;
             s2[i].a = ; s2[i].b = ;//最开始每个都是独立的，默认为链
         }
         bool flag = false;
         int n1, m1, n2, m2;

         scanf("%d%d", &n1, &m1);
         init(n1);
         for (int i = ; i<m1; i++)
         {
             int a, b;
             scanf("%d%d", &a, &b);
             int dx = find(a);
             int dy = find(b);
             if (dx != dy)
             {
                 pre[dx] = dy;
                 s1[dy].a += s1[dx].a;
                 s1[dx].a = ;//把拉手的孩子数量加起来，下同
             }
             else s1[dy].b = ;//否则在dy这个位置成环
         }

         scanf("%d%d", &n2, &m2);
         init(n2);
         for (int i = ; i<m2; i++)
         {
             int a, b;
             scanf("%d%d", &a, &b);
             int dx = find(a);
             int dy = find(b);
             if (dx != dy)
             {
                 pre[dx] = dy;
                 s2[dy].a += s2[dx].a;
                 s2[dx].a = ;
             }
             else s2[dy].b = ;
         }
         if (n1 == n2){

             sort(s1 + , s1 + n1 + , cmp);
             sort(s2 + , s2 + n2 + , cmp);//排序，若孩子的数量相同则对是否是环进行排序，这里要注意

             for (int i = ; i<n1; i++)
             if (s1[i].a != s2[i].a || s1[i].b != s2[i].b) {//判断数量，状态
                 flag = true;
                 break;
             }
         }
         if (n1 != n2)    flag = true;

         if (flag)
             printf("Case #%d: NO\n", cas++);
         else
             printf("Case #%d: YES\n", cas++);
     }
     return ;
 }