arrays – Ruby – 计算包含两个字符之一的数组中的字符串数

发布时间：2020-12-17 01:43:37 所属栏目：百科来源：网络整理

导读：我有这个数组： @a = ["P1 - D","P3 - M","P1 - D","P1 - M","P2 - D","P2 - M","P3 - D","P - D","Post - D","S1 - D","P1 - M"] 每个字符串都基于Page# – Device.所以P1 – D是：Page1 – 桌面 P3 – M是：Page3 – 移动如何找到数组中有多少字符串有D或

我有这个数组：

@a = ["P1 - D","P3 - M","P1 - D","P1 - M","P2 - D","P2 - M","P3 - D","P - D","Post - D","S1 - D","P1 - M"]

每个字符串都基于Page# – Device.所以P1 – D是：Page1 – 桌面& P3 – M是：Page3 – 移动

如何找到数组中有多少字符串有D或M？

解决方法

a.group_by { |e| e[-1] }.each_with_object({}) { |(k,v),hash| hash[k] = v.count }
#=> {"D"=>20,"M"=>7}

脚步：

groups = a.group_by { |e| e[-1] }
# {
#   "D"=> ["P1 - D","S1 - D"],#   "M"=> ["P3 - M","P1 - M"]
# }

group_counts = groups.each_with_object({}) { |(k,"M"=>7}

group_counts['M']
#=> 20

编辑

使用Ruby 2.4,您可以使用Hash#transform_values(积分转到Alex Golubenko :))：

a.group_by { |e| e[-1] }.transform_values(&:size)
#=> {"D"=>20,"M"=>7}

（编辑：李大同）

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