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

• Last Updated : 19 Mar, 2019

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

Example:

Input:
vec1 = {1, 45, 54, 71, 76, 12},
vec2 = {1, 7, 5, 4, 6, 12}
Output: {1, 12}

Input:
vec1 = {1, 7, 5, 4, 6, 12},
vec2 = {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 Vectors using STL`` ` `#include ``using` `namespace` `std;`` ` `int` `main()``{`` ` `    ``// Get the vector``    ``vector<``int``> vector1 = { 1, 45, 54, 71, 76, 12 };``    ``vector<``int``> vector2 = { 1, 7, 5, 4, 6, 12 };`` ` `    ``// Sort the vector``    ``sort(vector1.begin(), vector1.end());``    ``sort(vector2.begin(), vector2.end());`` ` `    ``// Print the vector``    ``cout << ``"First Vector: "``;``    ``for` `(``int` `i = 0; i < vector1.size(); i++)``        ``cout << vector1[i] << ``" "``;``    ``cout << endl;`` ` `    ``cout << ``"Second Vector: "``;``    ``for` `(``int` `i = 0; i < vector2.size(); i++)``        ``cout << vector2[i] << ``" "``;``    ``cout << endl;`` ` `    ``// Initialise a vector``    ``// to store the common values``    ``// and an iterator``    ``// to traverse this vector``    ``vector<``int``> v(vector1.size() + vector2.size());``    ``vector<``int``>::iterator it, st;`` ` `    ``it = set_intersection(vector1.begin(),``                          ``vector1.end(),``                          ``vector2.begin(),``                          ``vector2.end(),``                          ``v.begin());`` ` `    ``cout << ``"\nCommon elements:\n"``;``    ``for` `(st = v.begin(); st != it; ++st)``        ``cout << *st << ``", "``;``    ``cout << ``'\n'``;`` ` `    ``return` `0;``}`
Output:
```First Vector: 1 12 45 54 71 76
Second Vector: 1 4 5 6 7 12

Common elements:
1, 12,
```

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