相关疑难解决方法(0)

arr是字符串数组,例如:["hello", "world", "stack", "overflow", "hello", "again"].

什么是简单而优雅的方法来检查是否arr有重复,如果是,则返回其中一个(无论哪个).

例子:

["A", "B", "C", "B", "A"]    # => "A" or "B"
["A", "B", "C"]              # => nil

我有一个排序数组:

[
  'FATAL <error title="Request timed out.">',
  'FATAL <error title="Request timed out.">',
  'FATAL <error title="There is insufficient system memory to run this query.">'
]

我想得到这样的东西,但它不一定是哈希:

[
  {:error => 'FATAL <error title="Request timed out.">', :count => 2},
  {:error => 'FATAL <error title="There is insufficient system memory to run this query.">', :count => 1}
]

我有一个包含一些元素的数组.如何才能获得数组中每个元素的出现？

例:

鉴于:

a = ['cat', 'dog', 'fish', 'fish']

结果:

a2 #=> {'cat' => 1, 'dog' => 1, 'fish' => 2}

我怎样才能做到这一点？