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 vector1 = { 1, 45, 54, 71, 76, 12 };    vector 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 v(vector1.size() + vector2.size());    vector::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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