This is a problem available on hackerRank called Sales by Match. Let's solve it using python.

Problem Description

Alex works at a clothing store. There is a large pile of socks that must be paired by color for sale. Given an array of integers representing the color of each sock, determine how many pairs of socks with matching colors there are.

For example, there are n = 7 socks with colors ar = [1, 2, 1, 2, 1, 3, 2,] . There is one pair of color  and one of color . There are three odd socks left, one of each color. The number of pairs is .

Function Description

Complete the sockMerchant function in the editor below. It must return an integer representing the number of matching pairs of socks that are available.

sockMerchant has the following parameter(s):

  • n: the number of socks in the pile
  • ar: the colors of each sock

For more details about the problem visit: Sales by Match

Sample Input 

9
10 20 20 10 10 30 50 10 20

Sample Output 

3

I hope this may help you, Let me know if you got any better solution.