[프로그래머스] 위장

https://programmers.co.kr/learn/courses/30/lessons/42578

코딩테스트 연습 - 위장

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[ 나의 풀이 ]

공식을 찾아내는것이 포인트이다.

공식: (A+1)*(B+1) -1

import java.util.HashMap;
import java.util.Map;

class Solution {
    public int solution(String[][] clothes) {
        int answer = 1;
        
        Map<String, Integer> clothesMap = new HashMap<>();
        for(int i = 0; i < clothes.length; i++) {
            clothesMap.put(clothes[i][1], clothesMap.getOrDefault(clothes[i][1],0) + 1);
        }
        
        for(String cloth : clothesMap.keySet()) {
            answer *= (clothesMap.get(cloth) + 1);
        }
        return answer-1;
    }
}

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[ Iterator 사용 풀이 ]

import java.util.HashMap;
import java.util.Map;
import java.util.Iterator;

class Solution {
    public int solution(String[][] clothes) {
        int answer = 1;
        
        Map<String, Integer> clothesMap = new HashMap<>();
        for(int i = 0; i < clothes.length; i++) {
            clothesMap.put(clothes[i][1], clothesMap.getOrDefault(clothes[i][1],0) + 1);
        }
        
        Iterator<Integer> it = clothesMap.values().iterator();
        while(it.hasNext()) {
            answer *= (it.next().intValue() + 1);
        }
        return answer-1;
    }
}

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[ 람다 사용 풀이 ]

import java.util.Arrays;
import java.util.stream.Collectors;

class Solution {
    public int solution(String[][] clothes) {
        return Arrays.stream(clothes)
                .collect(Collectors.groupingBy(c -> c[1], Collectors.counting()))
                .values()
                .stream()
                .reduce(1L, (x, y) -> x * (y + 1)).intValue() -1;
    }
}