# How to find common elements between two Arrays using STL in C++?

Given two arrays, find common elements between these two arrays using STL in C++.

Example:

```Input:
arr1[] = {1, 45, 54, 71, 76, 12},
arr2[] = {1, 7, 5, 4, 6, 12}
Output: {1, 12}

Input:
arr1[] = {1, 7, 5, 4, 6, 12},
arr2[] = {10, 12, 11}
Output: {1, 4, 12}
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Common elements can be found with the help of set_intersection() function provided in STL.

Syntax:

```set_intersection (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
```

 `// C++ program to find common elements ` `// between two Arrays using STL ` ` `  `#include ` `using` `namespace` `std; ` ` `  `int` `main() ` `{ ` ` `  `    ``// Get the array ` `    ``int` `arr1[] = { 1, 45, 54, 71, 76, 12 }; ` `    ``int` `arr2[] = { 1, 7, 5, 4, 6, 12 }; ` ` `  `    ``// Compute the sizes ` `    ``int` `n1 = ``sizeof``(arr1) / ``sizeof``(arr1); ` `    ``int` `n2 = ``sizeof``(arr2) / ``sizeof``(arr2); ` ` `  `    ``// Sort the arrays ` `    ``sort(arr1, arr1 + n1); ` `    ``sort(arr2, arr2 + n2); ` ` `  `    ``// Print the array ` `    ``cout << ``"First Array: "``; ` `    ``for` `(``int` `i = 0; i < n1; i++) ` `        ``cout << arr1[i] << ``" "``; ` `    ``cout << endl; ` ` `  `    ``cout << ``"Second Array: "``; ` `    ``for` `(``int` `i = 0; i < n2; i++) ` `        ``cout << arr2[i] << ``" "``; ` `    ``cout << endl; ` ` `  `    ``// Initialise a vector ` `    ``// to store the common values ` `    ``// and an iterator ` `    ``// to traverse this vector ` `    ``vector<``int``> v(n1 + n2); ` `    ``vector<``int``>::iterator it, st; ` ` `  `    ``it = set_intersection(arr1, arr1 + n1, ` `                          ``arr2, arr2 + n2, ` `                          ``v.begin()); ` ` `  `    ``cout << ``"\nCommon elements:\n"``; ` `    ``for` `(st = v.begin(); st != it; ++st) ` `        ``cout << *st << ``", "``; ` `    ``cout << ``'\n'``; ` ` `  `    ``return` `0; ` `} `

Output:

```First Array: 1 12 45 54 71 76
Second Array: 1 4 5 6 7 12

Common elements:
1, 12,
```

Rated as one of the most sought after skills in the industry, own the basics of coding with our C++ STL Course and master the very concepts by intense problem-solving.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Improved By : shubham_singh

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.