创建一个新的 C++ 子向量？
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Creating a new C++ subvector?
提问by John Smith
Say I have a vector with values [1,2,3,4,5,6,7,8,9,10]. I want to create a new vector that refers to, for example, [5,6,7,8]. I imagine this is just a matter of creating a vector with pointers or do I have to push_back all the intermediary values I need?
假设我有一个值为 [1,2,3,4,5,6,7,8,9,10] 的向量。我想创建一个新的向量，例如，[5,6,7,8]。我想这只是用指针创建向量的问题，还是我必须推回我需要的所有中间值？
回答by hmjd
One of std::vector's constructor accepts a range:
其中之一std::vector的构造函数接受范围：
std::vector<int> v;
// Populate v.
for (int i = 1; i <= 10; i++) v.push_back(i);
// Construct v1 from subrange in v.
std::vector<int> v1(v.begin() + 4, v.end() - 2);
回答by Flexo
This is fairly easy to do with std::valarrayinstead of a vector:
这很容易做到std::valarray而不是向量：
#include <valarray>
#include <iostream>
#include <iterator>
#include <algorithm>
int main() {
const std::valarray<int> arr={0,1,2,3,4,5,6,7,8,9,10};
const std::valarray<int>& slice = arr[std::slice(5, // start pos
4, // size
1 // stride
)];
}
Which takes a "slice" of the valarray, more generically than a vector.
它需要 valarray 的“切片”，比向量更通用。
For a vector you can do it with the constructor that takes two iterators though:
对于向量，您可以使用带有两个迭代器的构造函数来完成：
const std::vector<int> arr={0,1,2,3,4,5,6,7,8,9,10};
std::vector<int> slice(arr.begin()+5, arr.begin()+9);
回答by Luchian Grigore
You don't have to use push_backif you don't want to, you can use std::copy:
你不必使用push_back，如果你不想，你可以使用std::copy：
std::vector<int> subvector;
copy ( v1.begin() + 4, v1.begin() + 8, std::back_inserter(subvector) );
回答by Taylor Southwick
I would do the following:
我会做以下事情：
#include <vector>
#include <iostream>
using namespace std;
void printvec(vector<int>& v){
for(int i = 0;i < v.size();i++){
cout << v[i] << " ";
}
cout << endl;
}
int main(){
vector<int> v;
for(int i = 1;i <= 10;i++) v.push_back(i);
printvec(v);
vector<int> v2(v.begin()+4, v.end()-2);
printvec(v2);
return 0;
}
~
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