프로그래머스 / 숫자 짝꿍

https://school.programmers.co.kr/learn/courses/30/lessons/131128

 

파이썬

억지스럽게... 

from collections import Counter
solution = lambda num1, num2: ('0' if (result := ''.join(each * inter_n[each] for each in sorted(inter_n, reverse=True)))[0] == '0' else result) if (inter_n := Counter(list(num1)) & Counter(list(num2))) else "-1"

덜 억지스럽게...

from collections import Counter


def solution(num1, num2):
    return ('0' if (result := ''.join(each * inter_n[each] for each in sorted(inter_n, reverse=True)))[
                       0] == '0' else result) if (inter_n := Counter(list(num1)) & Counter(list(num2))) else "-1"

& 연산자로 교집합의 원소 수까지 처리되는 것을 볼 수 있다.  

print(Counter(tuple(n1)), Counter(tuple(n2)), Counter(tuple(n1)) & Counter(tuple(n2)))
# Counter({'1': 2, '2': 2, '3': 1}) Counter({'4': 1, '2': 1, '5': 1, '3': 1, '1': 1}) Counter({'1': 1, '2': 1, '3': 1})

 

from collections import Counter


def solution(n1, n2):
    inter_n = Counter(tuple(n1)) & Counter(tuple(n2))
    if inter_n:
        result = ''.join(each * inter_n[each] for each in sorted(inter_n, reverse=True))
        return '0' if result[0] == '0' else result
    else:
        return '-1'

 

코틀린

코틀린에서는 Comparator.reverseOrder()으로 역순 정렬이 가능합니다. 
buildString은 내부적으로 StringBuilder를 생성하고, toString()을 자동호출 합니다.

import kotlin.math.min

class Solution {
    fun solution(x: String, y: String): String {
        val xMap = x.groupBy { it }.map { it.key to it.value.size }.toMap()
        val yMap = y.groupBy { it }.map { it.key to it.value.size }.toMap()
        val answer = buildString {
            xMap.keys.intersect(yMap.keys)
                .associateWith { min(xMap[it]!!, yMap[it]!!) }
                .toSortedMap(Comparator.reverseOrder())
                .map { (key, value) ->
                    repeat(value) {
                        append(key)
                    }
                }
        }
        return when {
            answer == "" -> "-1"
            answer[0] == '0' -> "0"
            else -> answer
        }
    }
}