[algo] 가장 큰수

1. 풀이

import java.util.*;
class Solution {
    public String solution(int[] numbers) {
        String answer = "";
        String[] arr = new String[numbers.length];
        for(int i=0; i < numbers.length; i++){
            arr[i] = String.valueOf(numbers[i]);
        }
         Arrays.sort(arr, new Comparator<String>() {
            @Override
            public int compare(String s1, String s2) {
                return (s2+s1).compareTo(s1+s2);
            }
        });
        if (arr[0].equals("0")) return "0";

        for (int i = 0; i < arr.length; i++) {
            answer+=arr[i];
        }
        
        
        return answer;
    }
}

2. 공부해볼것

1. Arrats.sort()
   정렬하는 함수인데 배열이 들어감
   하지만 Collection.reverseOrder() 사용은 Interger 값만 가능함
2. comporable compotor 비교
   https://makemethink.tistory.com/179

3. 다른사람 풀이

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

class Solution {
    public String solution(int[] numbers) {
        String answer = "";

        List<Integer> list = new ArrayList<>();
        for(int i = 0; i < numbers.length; i++) {
            list.add(numbers[i]);
        }
        Collections.sort(list, (a, b) -> {
            String as = String.valueOf(a), bs = String.valueOf(b);
            return -Integer.compare(Integer.parseInt(as + bs), Integer.parseInt(bs + as));
        });
        StringBuilder sb = _텍스트_new StringBuilder();
        for(Integer i : list) {
            sb.append(i);
        }
        answer = sb.toString();
        if(answer.charAt(0) == '0') {
            return "0";
        }else {
            return answer;
        }
    }
}