有两个集合，A集合内容为：{1、2、3、4}，B集合内容为：{1、2、5、6}，两个集合的对称差定义为A Δ B = (A − B) ∪(B − A)，上述A、B两集合的对称差为{3、4、5、6}。编写一个程序，用散列集求两个集合A、B的对称差集合，即求。-There are two sets, A collection of content: {1,2,3,4}, B contents of the collection is: {1,2,5,6}, the symmetric difference of two sets is defined as A Δ B = (A- B) ∪ (B- A), the A, B the symmetric difference of two sets is {3,4,5,6}. Write a program, set with the hash sum of two sets A, B the symmetric difference of sets, that is seeking.