1. 문제 설명

신고 결과 받기

2. 문제 분석

첫 번째 방법은 중복 방지를 위해 배열에서 contains로 계속해서 확인해주었다. 시간 초과는 나지 않았지만, 생각보다 비효율적이라는 생각이 들어 1. 이름을 키 값으로 한 배열 인덱스를 리턴하는 딕셔너리를 생성, 2. 해당 인덱스로 접근 가능한 집합 배열을 만들었다.

3. 나의 풀이

import Foundation

func solution(_ id_list:[String], _ report:[String], _ k:Int) -> [Int] {
    var reportDict = [String : [String]]()
    var reportCntDict = [String : Int]()
    var reportNames = Set<String>()
    for r in report {
        let r = r.split(separator: " ").map{String($0)}
        let (reporter, reported) = (r[0], r[1])
        let reportList = reportDict[reporter] ?? []
        if !reportList.contains(reported) {
            reportDict[reporter] = reportList + [reported]
            let reportCnt = reportCntDict[reported] ?? 0
            reportCntDict[reported] = reportCnt + 1
            if reportCnt + 1 >= k {
                reportNames.insert(reported)
            }
        }
    }
    
    var answers = [Int]()
    for reporter in id_list {
        let reportList = reportDict[reporter] ?? []
        let reportListSet = Set(reportList)
        let reportCnt = reportListSet.intersection(reportNames).count
        answers.append(reportCnt)
    }
    
    
    return answers
}

import Foundation

func solution(_ id_list:[String], _ report:[String], _ k:Int) -> [Int] {
    var nameDict = [String:Int]()
    for item in id_list.enumerated() {
        nameDict[item.element] = item.offset
    }
    var reportInfo = Array(repeating: Set<Int>(), count: id_list.count)
    
    for r in report {
        let r = r.split(separator: " ").map{String($0)}
        let (reporter, reported) = (nameDict[r[0]]!, nameDict[r[1]]!)
        reportInfo[reporter].insert(reported)
    }
    var reportList = Array(repeating: 0, count: id_list.count)
    for report in reportInfo {
        for id in report {
            reportList[id] += 1
        }
    }
    var reportResult = Set<Int>()
    for idx in 0..<reportList.count {
        let reportCnt = reportList[idx]
        if reportCnt >= k {
            reportResult.insert(idx)
        }
    }
    var answers = [Int]()
    
    for report in reportInfo {
        let cnt = report.intersection(reportResult).count
        answers.append(cnt)
    }
    return answers
}