在这种情况下,只要把print语句来执行这些代码,并与值。你会看到:
$ ruby -w t4.rb
t4.rb:21: warning: mismatched indentations at 'end' with 'while' at 10
initial array=[4, 3, 2, 1], initial position=2
last_pos=3
This is pass 2 cur=2 pre=3
after switching elements : [4, 2, 3, 1]
This is pass 3 cur=1 pre=3
after switching elements : [4, 2, 1, 3]
initial array=[4, 2, 1, 3], initial position=4
last_pos=3
initial array=[4, 2, 1, 3], initial position=4
last_pos=3
initial array=[4, 2, 1, 3], initial position=4
last_pos=3
initial array=[4, 2, 1, 3], initial position=4
last_pos=3
.......
t4.rb:2: stack level too deep (SystemStackError)
要停止递归,你需要检查一些条件。看看数百万个常用于解释递归的阶乘或斐波那契示例。
我不知道明白要如何排序,但此代码的工作:
def selectionSortRecursive(array, arrayPosition)
puts "initial array=#{array}, initial position=#{arrayPosition}"
initial_array_position = arrayPosition
last_pos = array.length - 1
puts "last_pos=#{last_pos}"
if arrayPosition == (last_pos)
puts "End of the line folks!"
return array
end
while arrayPosition >= 1 && arrayPosition <= last_pos && array[arrayPosition] < array[arrayPosition - 1] do
cur = array[arrayPosition]
pre = array[arrayPosition - 1]
puts "This is pass #{arrayPosition} cur=#{cur} pre=#{pre}"
if array[arrayPosition] < array[arrayPosition - 1]
tmp = array[arrayPosition]
array[arrayPosition] = array[arrayPosition - 1]
array[arrayPosition - 1] = tmp
puts "after switching elements : #{array}"
end # end if
arrayPosition += 1
end
selectionSortRecursive(array, arrayPosition) if arrayPosition != initial_array_position
return array
end
p selectionSortRecursive([4,3,2,1], 2)
执行:
$ ruby -w t4.rb
initial array=[4, 3, 2, 1], initial position=2
last_pos=3
This is pass 2 cur=2 pre=3
after switching elements : [4, 2, 3, 1]
This is pass 3 cur=1 pre=3
after switching elements : [4, 2, 1, 3]
initial array=[4, 2, 1, 3], initial position=4
last_pos=3
[4, 2, 1, 3]
没有递归调用,即函数永远不会调用本身? –
递归在哪里?在方法中没有调用selectionSortRecursive。 –
如果我运行'selectionSortRecursive([4,3,2,1],1)'我得到'未定义方法'<'为nil:NilClass'。您需要在while条件中添加&& arrayPosition <= array.length - 1'。 – BernardK