# How to Concatenate Two Vectors in C++?

Last Updated : 15 Feb, 2024

In C++, vectors are dynamic containers that can modify their size on insertion or deletion of elements during the runtime. It stores a collection of data in the contiguous memory location. In, this article we will learn how to merge two vectors in C++.

Example:

```Input:
myVector1={10, 30, 40}
myVector2 ={20, 50, 60}

Output:
myVector3 = {10,20,30,40,50,60}```

## Concatenate Two Vectors in C++

We can simply merge two vectors using the std::merge() function provided by the Standard Template Library (STL) of C++. The function merges two vectors into a single one in sorted order. We have to pass the iterator to the beginning and the end of the vector containers.

## C++

 `// C++ program to illustrate how to merge two vectors into a ` `// single one ` `#include ` `#include ` `#include ` ` `  `using` `namespace` `std; ` ` `  `int` `main() ` `{ ` `    ``// Define the input vectors ` ` `  `    ``vector<``int``> v1 = { 10, 30, 40 }; ` `    ``vector<``int``> v2 = { 20, 50, 60 }; ` ` `  `    ``// Print the original vectors ` `    ``cout << ``"Vector 1:"``; ` `    ``for` `(``int` `num : v1) { ` `        ``cout << num << ``" "``; ` `    ``} ` `    ``cout << endl; ` ` `  `    ``cout << ``"Vector 2:"``; ` `    ``for` `(``int` `num : v2) { ` `        ``cout << num << ``" "``; ` `    ``} ` `    ``cout << endl; ` ` `  `    ``// intialize a vector to accomodate elememnts from both ` `    ``// vectors ` ` `  `    ``vector<``int``> merged(v1.size() + v2.size()); ` ` `  `    ``// Merge the vectors using the merge function ` ` `  `    ``merge(v1.begin(), v1.end(), v2.begin(), v2.end(), ` `          ``merged.begin()); ` ` `  `    ``// Print the merged vector ` `    ``cout << ``"Merged Vector:"``; ` `    ``for` `(``int` `num : merged) { ` `        ``cout << num << ``" "``; ` `    ``} ` `    ``cout << endl; ` ` `  `    ``return` `0; ` `}`

Output

```Vector 1:10 30 40
Vector 2:20 50 60
Merged Vector:10 20 30 40 50 60
```

Time Complexity: O(N+M), where N and M are the lengths of both the vectors
Auxiliary Space: O(N+M)

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