如何使用STL对数组的元素（按3计数）进行微分？ [英] How to minupulate the elements (counting by 3) of an array usingSTL?
问题描述
我有一个整数数组。我需要找到数组中第0，第3，第6
，第9，...元素的最大值。我想知道STL（标准模板
库）是否提供了一种只操作数组的一部分的方法（而不是
整个），例如在这种情况下，0号，3号，6号，9号......请指教。谢谢。
Tony
Tony Young写道：我有一个整数数组。我需要找到数组中第0，第3，第6，第9 ......元素的最大值。我想知道STL（标准模板库）是否提供了一种只操纵数组的一部分（而不是整个）的方法，例如， 0,1,3,6,9 ......在这种情况下。
不，它不是。滚动你自己。
V
Victor Bazarov< v。******** @ comacast.net> ;写道：Tony Young写道：我有一个整数数组。我需要找到数组中第0，第3，第6，第9 ......元素的最大值。我想知道STL（标准模板库）是否提供了一种只操纵数组的一部分（而不是整个）的方法，例如， 0th，3th，6th，9th，......在这种情况下。
不，它不是。滚动你自己。
std :: valarray和std :: slice怎么样？事实上，可能有更好的方式，但我不经常使用valarrays（有人吗？）。
#include< iostream>
#include< valarray>
int main（）
{
const int N = 300;
int arr [N];
for（int i = 0; i< N; ++ i）{
arr [i] = i;
}
std :: valarray< int> varr（arr，N）;
std :: valarray< int> arr3 = varr [std :: slice（0，varr.size（）/ 3,3）];
std :: cout<< max = << arr3.max（）<< ''\\ n'';
}
-
Marcus Kwok
< br> <> blockquote> 2005-12-19，Marcus Kwok< ri ****** @ gehennom.net>写道：
Victor Bazarov< v。******** @ comacast.net>写道：Tony Young写道：我有一个整数数组。我需要找到数组中第0，第3，第6，第9 ......元素的最大值。我想知道STL（标准模板库）是否提供了一种方法来操纵数组的一部分（而不是整数），例如0th，3th，6th
，9th，......在这种情况下。
不，它不是。滚动你自己。
std :: valarray和std :: slice怎么样？事实上，可能有更好的方法，但我不经常使用valarrays（是否有人？）。
它'这是标准库中包含的内容之一，其中很难理解。 B.Stroustrup在
_TCPL_中给出了类似这样的内容，但它对我来说没有启发：为
计算优化的向量。嗯？
我的决定是，如果我需要它，我会知道他的意思，
所以我忽略了valarrays。
-
Neil Cerutti
Hi,
I have an array of integer. I need to find the max of the 0th, 3th, 6th
, 9th, ... elements in the array. I wonder if STL (standard template
library) provides a way to manipulate only part of an array (rather than
whole), e.g. 0th, 3th, 6th , 9th, ... in this case. Please advise. Thanks.
Tony
Tony Young wrote:I have an array of integer. I need to find the max of the 0th, 3th,
6th , 9th, ... elements in the array. I wonder if STL (standard
template library) provides a way to manipulate only part of an array
(rather than whole), e.g. 0th, 3th, 6th , 9th, ... in this case.
No, it doesn''t. Roll your own.
V
Victor Bazarov <v.********@comacast.net> wrote:Tony Young wrote:I have an array of integer. I need to find the max of the 0th, 3th,
6th , 9th, ... elements in the array. I wonder if STL (standard
template library) provides a way to manipulate only part of an array
(rather than whole), e.g. 0th, 3th, 6th , 9th, ... in this case.
No, it doesn''t. Roll your own.
What about std::valarray and std::slice? In fact, there may be a better
way, but I do not use valarrays very often (does anybody?).
#include <iostream>
#include <valarray>
int main()
{
const int N = 300;
int arr[N];
for (int i = 0; i < N; ++i) {
arr[i] = i;
}
std::valarray<int> varr(arr, N);
std::valarray<int> arr3 = varr[std::slice(0, varr.size() / 3, 3)];
std::cout << "max = " << arr3.max() << ''\n'';
}
--
Marcus Kwok
On 2005-12-19, Marcus Kwok <ri******@gehennom.net> wrote:Victor Bazarov <v.********@comacast.net> wrote:Tony Young wrote:I have an array of integer. I need to find the max of the
0th, 3th, 6th , 9th, ... elements in the array. I wonder if
STL (standard template library) provides a way to manipulate
only part of an array (rather than whole), e.g. 0th, 3th, 6th
, 9th, ... in this case.
No, it doesn''t. Roll your own.
What about std::valarray and std::slice? In fact, there may be
a better way, but I do not use valarrays very often (does
anybody?).
It''s one of the things included in the standard library that''s
hard to understand. B.Stroustrup puts it something like this in
_TCPL_, but it was unenlightening to me: A vector optimized for
computations. Huh?
My decision was that if I needed it I would know what he meant,
so I ignored valarrays.
--
Neil Cerutti
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