[HackerRank] Preparation_Kit (01. Sales by Match)

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

Example
n = 7

ar = [1,2,1,2,1,3,2]

There is one pair of color 1 and one of color 2. There are three odd socks left, one of each color.

The number of pairs is 2.

Function Description

Complete the sockMerchant function in the editor below.

sockMerchant has the following parameter(s):

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

Returns

• int: the number of pairs

Input Format

The first line contains an integer n, the number of socks represented in ar.
The second line contains n space-separated integers, ar[i], the colors of the socks in the pile.

Constraints

• 1 <= n <= 100
• 1 <= ar[i] <= 100 where 0 <= i < n

Sample Input

STDIN                       Function
-----                       --------
9                           n = 9
10 20 20 10 10 30 50 10 20  ar = [10, 20, 20, 10, 10, 30, 50, 10, 20]

Sample Output

3

Explanation

There are three pairs of socks.

import Foundation

/*
 * Complete the 'sockMerchant' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts following parameters:
 *  1. INTEGER n
 *  2. INTEGER_ARRAY ar
 */

func sockMerchant(n: Int, ar: [Int]) -> Int {
    // Write your code here
    var ans = 0
    var dic: [Int: Int] = [:]
    for a in ar {
        if dic.contains{$0.key == a} {
            ans += 1
            dic.removeValue(forKey: a)
        } else {
            dic[a] = 0
        }
    }
    return ans
}

let stdout = ProcessInfo.processInfo.environment["OUTPUT_PATH"]!
FileManager.default.createFile(atPath: stdout, contents: nil, attributes: nil)
let fileHandle = FileHandle(forWritingAtPath: stdout)!

guard let n = Int((readLine()?.trimmingCharacters(in: .whitespacesAndNewlines))!)
else { fatalError("Bad input") }

guard let arTemp = readLine()?.replacingOccurrences(of: "\\s+$", with: "", options: .regularExpression) else { fatalError("Bad input") }

let ar: [Int] = arTemp.split(separator: " ").map {
    if let arItem = Int($0) {
        return arItem
    } else { fatalError("Bad input") }
}

guard ar.count == n else { fatalError("Bad input") }

let result = sockMerchant(n: n, ar: ar)

fileHandle.write(String(result).data(using: .utf8)!)
fileHandle.write("\n".data(using: .utf8)!)

 

contains(where: (Dictionary<Int, Int>.Element) throws -> Bool // {$0.key == }

dic.removeValue(forKey: a) // key & value 삭제

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https://www.hackerrank.com/challenges/sock-merchant/problem?isFullScreen=true&h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=warmup