如何合并两个字符串数组的哈希值

Question

如何在以下条件下合并两个哈希值：

# 1º case
  a = {}
  b = { "1"=>["c1", "c2"], "2"=>["c2","c3"] }
  # merging a and b
# a = { "1"=>["c1", "c2"], "2"=>["c2","c3"] } 

# 2º case
  a = { "1"=>["c1", "c2"], "2"=>["c2","c3"] } 
  c = { "1"=>["c1", "c3"], "3"=>["c5"] }
  # merging a and c   
# a = { "1"=>["c1", "c2", "c3"], "2"=>["c2","c3"], "3"=>["c5"] }

到目前为止我得到了什么：

对于数组，我知道可以与运算符“|”合并

a = ["c0", "c1"], b = ["c1", "c2"]
a = a | b
# a = ["c0", "c1", "c2"]

但是哈希不起作用：

a.merge(b){ |key, oldval, newval| oldval | newval }
# returns whatever was in the first place for the Hash a

S.O中有答案（实际上其中一个使用上面的相同示例），但我无法使其工作（我也尝试与非空哈希合并）。我知道我可以在循环中打开等等......但我正在寻找“红宝石”的方式。

提前致谢。