在Rby中以相反的顺序对数组进行排序
Sorting arrays in opposite order in Rby
我是 Ruby 的新手，需要一段代码向我解释。要排序的数组是这个：
books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia",
"A Brief History of Time", "A Wrinkle in Time"]
下面的代码块对该数组进行排序 books A-Z
books.sort! { |firstBook, secondBook| firstBook <=> secondBook }
下面的代码块对该数组进行排序 books Z-A
books.sort! { |firstBook, secondBook| secondBook <=> firstBook }
这是为什么？为什么第一个排序 A-Z 而第二个排序 Z-A？我有点理解组合比较运算符 <=>。它 returns -1、1 或 0 取决于比较。但是，这是如何排序的呢？谢谢！
排序运算符看起来像这样：它告诉您某个对象是否小于、大于或等于排序顺序中的另一个对象。所以你的第一个块问 "Is firstBook before or after secondBook"，第二个块问 "is secondBook is before or after first book"。如您所见，答案是相反的：
- "A"在之前 "B" (
"A" <=> "B" == -1)
- "B"在之后 "A" (
"B" <=> "A" == 1)
所以如果你颠倒问题的顺序，你会得到相反的答案，这意味着（比较类型）sort algorithm给出相反的结果。
排序算法使用块中的 return 值，在本例中它是比较运算符 (<=>) 的结果。当 -1 为 return 时，a 和 b 的顺序将保持不变（即 a 在 b 之前，具体取决于算法的值将保留 a 和 b 的当前顺序以了解 a 应该排在 b 之前（-1），还是排在之后（1), 或者两者等价 (0).
算法反复比较相邻的元素对，直到所有元素都有序。
让我们添加一些输出，看看当您对图书列表调用 sort 时会发生什么。这将使我们对排序方法的作用有所了解。我添加了注释来说明排序的每个步骤如何改变 books 数组。请注意，在本示例中讨论如何简化排序 "swaps" 个位置。
> books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]
> books.sort! do |a, b|
> result = a <=> b
> puts %(\n"#{ a }" <=> "#{ b }" #=> #{ result }) # Print out which elements are being compared and the result
> result
> end
"Charlie and the Chocolate Factory" <=> "War and Peace" #=> -1
# ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"] *** No change
"War and Peace" <=> "Utopia" #=> 1
# ["Charlie and the Chocolate Factory", "Utopia", "War and Peace", "A Brief History of Time", "A Wrinkle in Time"] *** Positions of "Utopia" and "War and Peace" are swapped
"Charlie and the Chocolate Factory" <=> "Utopia" #=> -1
# ["Charlie and the Chocolate Factory", "Utopia", "War and Peace", "A Brief History of Time", "A Wrinkle in Time"] *** No change
"War and Peace" <=> "A Brief History of Time" #=> 1
# ["Charlie and the Chocolate Factory", "Utopia", "A Brief History of Time", "War and Peace", "A Wrinkle in Time"] *** Positions of "War and Peace" and "A Brief History of Time" are swapped
"Utopia" <=> "A Brief History of Time" #=> 1
# ["Charlie and the Chocolate Factory", "A Brief History of Time", "Utopia", "War and Peace", "A Wrinkle in Time"] *** Positions of "Utopia" and "A Brief History of Time" are swapped
"Charlie and the Chocolate Factory" <=> "A Brief History of Time" #=> 1
# ["A Brief History of Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace", "A Wrinkle in Time"] *** Positions of "Charlie and the Chocolate Factory" and "A Brief History of Time" are swapped
"War and Peace" <=> "A Wrinkle in Time" #=> 1
# ["A Brief History of Time", "Charlie and the Chocolate Factory", "Utopia", "A Wrinkle in Time", "War and Peace"] *** Positions of "War and Peace" and "A Wrinkle in Time" are swapped
"Utopia" <=> "A Wrinkle in Time" #=> 1
# ["A Brief History of Time", "Charlie and the Chocolate Factory", "A Wrinkle in Time", "Utopia", "War and Peace"] *** Positions of "Utopia" and "A Wrinkle in Time" are swapped
"Charlie and the Chocolate Factory" <=> "A Wrinkle in Time" #=> 1
# ["A Brief History of Time", "A Wrinkle in Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace"] *** Positions of "Charlie and the Chocolate Factory" and "A Wrinkle in Time" are swapped
"A Brief History of Time" <=> "A Wrinkle in Time" #=> -1
# ["A Brief History of Time", "A Wrinkle in Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace"] *** No change
# Done! All elements have been sorted, so the algorithm exits.
=> ["A Brief History of Time", "A Wrinkle in Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace"]
当比较从 a <=> b 更改为 b <=> a 时，结果会反转，从而导致排序以相反的顺序进行。
> books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]
> books.sort! do |a, b|
> result = b <=> a
> puts %(\n"#{ b }" <=> "#{ a }" #=> #{ result }) # Print out which elements are being compared and the result
> result
> end
"A Wrinkle in Time" <=> "A Brief History of Time" #=> 1
"Charlie and the Chocolate Factory" <=> "A Brief History of Time" #=> 1
"Charlie and the Chocolate Factory" <=> "A Wrinkle in Time" #=> 1
"Utopia" <=> "A Brief History of Time" #=> 1
"Utopia" <=> "A Wrinkle in Time" #=> 1
"Utopia" <=> "Charlie and the Chocolate Factory" #=> 1
"War and Peace" <=> "A Brief History of Time" #=> 1
"War and Peace" <=> "A Wrinkle in Time" #=> 1
"War and Peace" <=> "Charlie and the Chocolate Factory" #=> 1
"War and Peace" <=> "Utopia" #=> 1
=> ["War and Peace", "Utopia", "Charlie and the Chocolate Factory", "A Wrinkle in Time", "A Brief History of Time"]
另请参阅 Array#sort!
的文档
我是 Ruby 的新手，需要一段代码向我解释。要排序的数组是这个：
books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia",
"A Brief History of Time", "A Wrinkle in Time"]
下面的代码块对该数组进行排序 books A-Z
books.sort! { |firstBook, secondBook| firstBook <=> secondBook }
下面的代码块对该数组进行排序 books Z-A
books.sort! { |firstBook, secondBook| secondBook <=> firstBook }
这是为什么？为什么第一个排序 A-Z 而第二个排序 Z-A？我有点理解组合比较运算符 <=>。它 returns -1、1 或 0 取决于比较。但是，这是如何排序的呢？谢谢！
排序运算符看起来像这样：它告诉您某个对象是否小于、大于或等于排序顺序中的另一个对象。所以你的第一个块问 "Is firstBook before or after secondBook"，第二个块问 "is secondBook is before or after first book"。如您所见，答案是相反的：
- "A"在之前 "B" (
"A" <=> "B" == -1) - "B"在之后 "A" (
"B" <=> "A" == 1)
所以如果你颠倒问题的顺序，你会得到相反的答案，这意味着（比较类型）sort algorithm给出相反的结果。
排序算法使用块中的 return 值，在本例中它是比较运算符 (<=>) 的结果。当 -1 为 return 时，a 和 b 的顺序将保持不变（即 a 在 b 之前，具体取决于算法的值将保留 a 和 b 的当前顺序以了解 a 应该排在 b 之前（-1），还是排在之后（1), 或者两者等价 (0).
算法反复比较相邻的元素对，直到所有元素都有序。
让我们添加一些输出，看看当您对图书列表调用 sort 时会发生什么。这将使我们对排序方法的作用有所了解。我添加了注释来说明排序的每个步骤如何改变 books 数组。请注意，在本示例中讨论如何简化排序 "swaps" 个位置。
> books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]
> books.sort! do |a, b|
> result = a <=> b
> puts %(\n"#{ a }" <=> "#{ b }" #=> #{ result }) # Print out which elements are being compared and the result
> result
> end
"Charlie and the Chocolate Factory" <=> "War and Peace" #=> -1
# ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"] *** No change
"War and Peace" <=> "Utopia" #=> 1
# ["Charlie and the Chocolate Factory", "Utopia", "War and Peace", "A Brief History of Time", "A Wrinkle in Time"] *** Positions of "Utopia" and "War and Peace" are swapped
"Charlie and the Chocolate Factory" <=> "Utopia" #=> -1
# ["Charlie and the Chocolate Factory", "Utopia", "War and Peace", "A Brief History of Time", "A Wrinkle in Time"] *** No change
"War and Peace" <=> "A Brief History of Time" #=> 1
# ["Charlie and the Chocolate Factory", "Utopia", "A Brief History of Time", "War and Peace", "A Wrinkle in Time"] *** Positions of "War and Peace" and "A Brief History of Time" are swapped
"Utopia" <=> "A Brief History of Time" #=> 1
# ["Charlie and the Chocolate Factory", "A Brief History of Time", "Utopia", "War and Peace", "A Wrinkle in Time"] *** Positions of "Utopia" and "A Brief History of Time" are swapped
"Charlie and the Chocolate Factory" <=> "A Brief History of Time" #=> 1
# ["A Brief History of Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace", "A Wrinkle in Time"] *** Positions of "Charlie and the Chocolate Factory" and "A Brief History of Time" are swapped
"War and Peace" <=> "A Wrinkle in Time" #=> 1
# ["A Brief History of Time", "Charlie and the Chocolate Factory", "Utopia", "A Wrinkle in Time", "War and Peace"] *** Positions of "War and Peace" and "A Wrinkle in Time" are swapped
"Utopia" <=> "A Wrinkle in Time" #=> 1
# ["A Brief History of Time", "Charlie and the Chocolate Factory", "A Wrinkle in Time", "Utopia", "War and Peace"] *** Positions of "Utopia" and "A Wrinkle in Time" are swapped
"Charlie and the Chocolate Factory" <=> "A Wrinkle in Time" #=> 1
# ["A Brief History of Time", "A Wrinkle in Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace"] *** Positions of "Charlie and the Chocolate Factory" and "A Wrinkle in Time" are swapped
"A Brief History of Time" <=> "A Wrinkle in Time" #=> -1
# ["A Brief History of Time", "A Wrinkle in Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace"] *** No change
# Done! All elements have been sorted, so the algorithm exits.
=> ["A Brief History of Time", "A Wrinkle in Time", "Charlie and the Chocolate Factory", "Utopia", "War and Peace"]
当比较从 a <=> b 更改为 b <=> a 时，结果会反转，从而导致排序以相反的顺序进行。
> books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]
> books.sort! do |a, b|
> result = b <=> a
> puts %(\n"#{ b }" <=> "#{ a }" #=> #{ result }) # Print out which elements are being compared and the result
> result
> end
"A Wrinkle in Time" <=> "A Brief History of Time" #=> 1
"Charlie and the Chocolate Factory" <=> "A Brief History of Time" #=> 1
"Charlie and the Chocolate Factory" <=> "A Wrinkle in Time" #=> 1
"Utopia" <=> "A Brief History of Time" #=> 1
"Utopia" <=> "A Wrinkle in Time" #=> 1
"Utopia" <=> "Charlie and the Chocolate Factory" #=> 1
"War and Peace" <=> "A Brief History of Time" #=> 1
"War and Peace" <=> "A Wrinkle in Time" #=> 1
"War and Peace" <=> "Charlie and the Chocolate Factory" #=> 1
"War and Peace" <=> "Utopia" #=> 1
=> ["War and Peace", "Utopia", "Charlie and the Chocolate Factory", "A Wrinkle in Time", "A Brief History of Time"]
另请参阅 Array#sort!
的文档