数组操作...变得更简单了吗? [英] Array Manipulation ... made simpler?

问题描述

嘿，

快速提问，随时向我指出课程或常见问题解答.有更快或更有效的方法来执行以下操作吗?只需将值沿数组向下滑动即可:

Hey,

Quick question, and feel free to just point me at a class or FAQ. Is there a faster or more efficient way to do the following? Just slide values down an array:

int a[5] = {1, 2, 5, 2, 1};

a[4] = a[3];
a[3] = a[2];
a[2] = a[1];
a[1] = a[0];

a[0] = //Some input

我只是在寻找一种将所有值向下滑动1位的方法.预先感谢您回答我的琐碎问题.

I''m just looking for a way to slide all the values down by 1 place. Thanks in advance for answering my trivial question.

推荐答案

使用集合而不是数组.如果不能这样做，请分配一个大一个元素的新数组，然后将另一个数组移到新数组中，该数组从新数组中的元素1开始.

Use a collection instead of an array. If you can''t do that, allocate a new array that''s one element larger, and then move the other array into the new one starting at element 1 in the new array.

其中有oldie-goldie memmove [

There is the oldie-goldie memmove[^]:

#include <cstring>
  //...
  int a[5] = {1, 2, 5, 2, 1};
  memmove(&a[1], &a[0], sizeof(a)-sizeof(a[0]));

像memmove 这样的调用最有可能被优化以利用块内存移动内在操作，尽管一个不错的编译器会看到您的for -loop(或顺序代码(无论您拥有什么)，并在编译过程中将其替换为memmove .如果这是一个主要因素，则可以运行一些性能测试，尽管如果仅是数百或什至1000个您正在谈论的元素，则可能无关紧要.

Calls like memmove will most likely be optimized to take advantage of block-memory move intrinsic operations, although a decent compiler would see your for-loop (or sequential code, whatever you have), and replace it with a memmove during compilation. You could run some performance tests if this is a major factor, although if it''s just a few hundred or even 1000 elements you are talking about, it probably does not matter much.

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