我有这样的事情:红宝石路值
a = [{"group_id" => 1, "student_id" => 3, "candies" => 4},
{"group_id" => 2, "student_id" => 1, "candies" => 3},
{"group_id" => 1, "student_id" => 2, "candies" => 2},
{"group_id" => 3, "student_id" => 4, "candies" => 6},
{"group_id" => 1, "student_id" => 5, "candies" => 1},
{"group_id" => 3, "student_id" => 6, "candies" => 1},
{"group_id" => 4, "student_id" => 8, "candies" => 3}]
我有三组学生,每个学生得到一定数量的糖果。我想统计一组糖果的总数。为此,我需要了解属于某个团体的学生并积累他们的糖果。我可以使用循环和初始化计数为零它:
aa = a.group_by { |a| a["group_id"] }
# =>
{
1 => [
{"group_id"=>1, "student_id"=>3, "candies"=>4},
{"group_id"=>1, "student_id"=>2, "candies"=>2},
{"group_id"=>1, "student_id"=>5, "candies"=>1}
],
2 => [{"group_id"=>2, "student_id"=>1, "candies"=>3}],
3 => [
{"group_id"=>3, "student_id"=>4, "candies"=>6},
{"group_id"=>3, "student_id"=>6, "candies"=>1}
],
4 => [{"group_id"=>4, "student_id"=>8, "candies"=>3}]
}
但我不能够在group_id
内累积值。我想知道是否有任何简洁的表示方式。我如何总结一组中存在的糖果总数?
什么是三组和四'group_id's之间的关系? – sawa
b/w他们没有关系。 – shashydhar
那么问题中提到的群体是什么?这完全不清楚。 – sawa