Question

我想生成一个数组，然后遍历它多次，并根据它们的状态对数组中的项目进行更改。我无法使条件语句正常工作

lockers = Array.new(900, "Closed");

#walk through and change every other item to "closed" if it is "open", and 
"open" if it is "closed
(1...lockers.size).step(2).each { |i| 
if lockers[i] = "Open"
lockers[i] = "Closed";

elsif (lockers[i] = "Closed")
lockers[i] = "Open";
end

lockers.join };


#walk through and change every 3rd item to "closed" if it is "open", and 
"open" if it is "closed
(0...lockers.size).step(3).each { |i| 
if (lockers[i] = "Open")
lockers[i] = "Closed";

elsif (lockers[i] = "Closed")
lockers[i] = "Open";
end

lockers.join; };

#walk through and change every 4th item to "closed" if it is "open", and "open" if it is "closed
(0...lockers.size).step(4).each { |i| 
if (lockers[i] = "Open")
lockers[i] = "Closed";

elsif (lockers[i] = "Closed")
lockers[i] = "Open";
end

lockers.join; };

执行上述操作将正确地制作数组，并将所有内容都设置为“ Closed”。第一次遍历后，它无法将任何项目更改为“打开”。

如果我将条件更改为“ lockers [i] =“打开””，则显然可行。但是后来的条件语句也无法提取应有的每个项目。

Answer 1

这是您可以做到的一种方法。

def flip(lockers, n)
  h = { "closed"=>"open", "open"=>"closed" }
  (0..lockers.size-1).step(n).each { |i| lockers[i] = h[lockers[i]] }
  lockers
end

lockers = 6.times.map { ["open", "closed"].sample }
  #=> ["open", "closed", "open", "closed", "closed", "open"]

flip(lockers, 2)
  #=> ["closed", "closed", "closed", "closed", "open", "open"]
lockers
  #=> ["closed", "closed", "closed", "closed", "open", "open"] 

lockers = ["open", "closed", "open", "closed", "closed", "open"] 
flip(lockers, 3) 
  #=> ["closed", "closed", "open", "open", "closed", "open"]

lockers = ["open", "closed", "open", "closed", "closed", "open"] 
flip(lockers, 4) 
  #=> ["closed", "closed", "open", "closed", "open", "open"]

以下是另一种方式。

def flip(lockers, n)
  h = { "closed"=>"open", "open"=>"closed" }
  lockers.map!.with_index { |s,i| (i % n).zero? ? h[s] : s }
end

我假设通过“其他所有项目”，要翻转的第一个元素是数组的第一个元素。（请注意，数组的最后一个元素的索引为lockers.size-1，而不是lockers.size。）

我了解您希望修改现有阵列，所以这就是我所做的。要返回一个新数组并保持原始数组不变（通常是首选做法），只需将map!替换为map。

请参见Array#map!和 Array#map。

需要一些帮助来遍历数组并进行条件更改

1 个答案: