Extract a subvector from a vector in C++

This post will discuss how to extract a subvector from a vector in C++.

1. Using range constructor

The range constructor creates a new vector containing all elements from the specified range. To extract a subvector from a vector, pass the iterators to the starting and the ending positions of the subvector. This is demonstrated below:

#include <iostream>

#include <vector>

#include <algorithm>

int main()

{

std::vector<int> v = {1, 2, 3, 4, 5, 6, 7, 8};

int start = 2;

int end = 4;

std::vector<int> slice(v.begin() + start, v.begin() + end + 1);

for (int &i: slice) {

std::cout << i << ' ';

}

return 0;

}

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Output:

2 3 4

2. Using `std::vector::insert`

For an existing vector, we can use the std::vector::insert member function that takes an iterator to the destination vector and iterators specifying the range of the vector elements. A typical invocation for this function would look like:

#include <iostream>

#include <vector>

#include <algorithm>

int main()

{

std::vector<int> v = {1, 2, 3, 4, 5, 6, 7, 8};

int start = 2;

int end = 4;

std::vector<int> slice;

slice.insert(slice.begin(), v.begin() + start, v.begin() + end + 1);

for (int &i: slice) {

std::cout << i << ' ';

}

return 0;

}

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Output:

2 3 4

3. Using `std::copy`

Another option is to use the std::copy standard algorithm to copy all elements of the specified range to another vector. Here’s how the code would look like:

#include <iostream>

#include <vector>

#include <algorithm>

int main()

{

std::vector<int> v = {1, 2, 3, 4, 5, 6, 7, 8};

int start = 2;

int end = 4;

std::vector<int> slice;

std::copy(v.begin() + start, v.begin() + end + 1, std::back_inserter(slice));

for (int &i: slice) {

std::cout << i << ' ';

}

return 0;

}

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Output:

2 3 4

4. Using `std::vector::assign`

Finally, we can use the std::vector::assign member function to replace the vector contents with elements in the specified range. The following C++ program demonstrates it:

#include <iostream>

#include <vector>

#include <algorithm>

int main()

{

std::vector<int> v = {1, 2, 3, 4, 5, 6, 7, 8};

int start = 2;

int end = 4;

std::vector<int> slice;

slice.assign(v.begin() + start, v.begin() + end + 1);

for (int &i: slice) {

std::cout << i << ' ';

}

return 0;

}

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Output:

2 3 4

That’s all about extracting a subvector from a vector in C++.

Extract a subvector from a vector in C++

1. Using range constructor

2. Using std::vector::insert

3. Using std::copy

4. Using std::vector::assign

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2. Using `std::vector::insert`

3. Using `std::copy`

4. Using `std::vector::assign`