[알고리즘] 21. Sock Merchant

John works at a clothing store. He has a large pile of socks that he must pair 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  socks with colors . 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

Input Format

The first line contains an integer , the number of socks represented in .
The second line contains  space-separated integers describing the colors  of the socks in the pile.

Constraints

•  where 

Output Format

Return the total number of matching pairs of socks that John can sell.

Sample Input

9
10 20 20 10 10 30 50 10 20

Sample Output

3

Explanation

John can match three pairs of socks.

답 : 

#!/bin/python3

import math

import os

import random

import re

import sys

from collections import Counter

# Complete the sockMerchant function below.

def sockMerchant(n, ar):

ar = dict(Counter(ar))

count = 0

for col,freq in ar.items():

if freq >= 2:

count += int(freq /2)

return count

if __name__ == '__main__':

fptr = open(os.environ['OUTPUT_PATH'], 'w')

n = int(input())

ar = list(map(int, input().rstrip().split()))

result = sockMerchant(n, ar)

fptr.write(str(result) + '\n')

fptr.close()

양말의 쌍을 세서 쌍의 수를 출력하는 문제! 

dict형태로 바꾼 후, for문을 돌면서 freq를 2로 나눈 몫을 count에 추가했다