[Swift 알고리즘] 한 번만 등장한 문자

 

 

import Foundation

func solution(_ s:String) -> String {
    var targetDict:[String:Int] = [:]
    var resArr:[String] = []
    for i in s.map{String($0)} {
        if targetDict.keys.contains(i) {
            targetDict[i]! += 1
            continue
        }
        targetDict[i] = 1
    }
    _ = targetDict.map{ curKey, curVal in
        if curVal == 1 {
            resArr.append(curKey)
        }
    }
    return resArr.sorted(by: <).joined(separator: "")
}