Write a function

that given two vectors *X* and *Y* in increasing order, returns
the number of common elements in the two vectors, that is, the number
of integer numbers *a* such that *a*=*X*[*i*]=*Y*[*j*] for any *i* and *j*.

**Precondition**

The two vectors are in strictly increasing order.

**Samples**

*common_elements*([3,5,7,8], [2,3,7,9,10]) = 2.

*common_elements*([1,2,3,4,5], [3,4,5,6,7,8]) = 3.

*common_elements*([1,2,3,4,5], [8,9]) = 0.

Information

- Author
- Jordi Petit
- Language
- English
- Translator
- Carlos Molina
- Original language
- Catalan
- Other languages
- Catalan
- Official solutions
- C++
- User solutions
- C++