循环中的最后一个元素是否应该单独处理？ [英] Does the last element in a loop deserve a separate treatment?

问题描述

  i = begin 
 while（i！=结束）{
 // ...做东西
 if（i == end-1（one-but-last element））{
 ...做其他的东西
} 
增量i 
} 
  

然后我问这个问题：写这个？

  i = begin 
 mid =（end  -  begin）/ 2 //（中间元素） 
 while（i！= end）{
 // ...做东西
 if（i> mid）{
 ...做其他的东西
} 
增量i 
} 
  

在我看来，这打击了写作的意图一个循环：循环，因为每个元素都有一些共同点。使用这个构造，对于你做一些不同的元素。所以，我得出结论，你需要一个单独的循环为这些元素：

$ p $ code i =开始）/ 2 //（中间元素）
while（i！= mid）{
// ...做东西
增量i
}

while（i！= end）{
// ...做东西
// ...做其他的东西
增量的i
}

现在我甚至看到了问题关于如何编写如果 - 条款以一个很好的方式...我伤心：这里不对。

我错了吗？如果是这样的话，那么在编码的时候，你会发现什么是特殊情况下的混乱循环体呢？

> @xtofl，

我同意你的关注。百万倍我碰到过类似的问题。

任何一个开发人员都会为第一个元素或最后一个元素添加特殊处理。

在大多数情况下，值得从 startIdx + 1 或者 endIdx - 1 元素循环，甚至将一个长循环拆分成多个较短的循环。

在我看来，不常见的 / em>只要有可能就应该在循环之外处理。

When reviewing, I sometimes encounter this kind of loop:

i = begin
while ( i != end ) {    
   // ... do stuff
   if ( i == end-1 (the one-but-last element) ) {
      ... do other stuff
   }
   increment i
}

Then I ask the question: would you write this?

i = begin
mid = ( end - begin ) / 2 // (the middle element)
while ( i != end ) {    
   // ... do stuff
   if ( i > mid ) {
      ... do other stuff
   }
   increment i
}

In my opinion, this beats the intention of writing a loop: you loop because there is something common to be done for each of the elements. Using this construct, for some of the elements you do something different. So, I conclude, you need a separate loop for those elements:

i = begin
mid = ( end - begin ) / 2 //(the middle element)
while ( i != mid ) {    
   // ... do stuff
   increment i
}

while ( i != end ) {
   // ... do stuff
   // ... do other stuff
   increment i
}

Now I even saw a question on SO on how to write the if-clause in a nice way... And I got sad: something isn't right here.

Am I wrong? If so, what's so good about cluttering the loop body with special cases, which you are aware of upfront, at coding time?

解决方案

@xtofl,

I agree with your concern.

Million times I encountered similar problem.

Either developer adds special handling for first or for last element.

In most cases it is worth to just loop from startIdx + 1 or to endIdx - 1 element or even split one long loop into multiple shorter loops.

In a very rare cases it's not possible to split loop.

In my opinion uncommon things should be handled outside of the loop whenever possible.

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