[Programmers]정렬-가장큰수

package com.hyosung.algo;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;


// 정렬 - 가장큰수 level.2
public class pro_sort_p02 {

    static int[] buff;
    static boolean[] visited;



    public static void main(String[] args) {

        //int[] numbers = {6,10,2};

        int[] numbers = {3,30,34,5,9};
        //int[] numbers = {0,4,1};


        String result = solution(numbers);
        System.out.println("result: " + result);
    }


    static void viewArray(int[] a) {
        for(int i=0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }
    }

    static void viewStrArray(String[] a) {

        for(int i=0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }

    }


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

        String[] str = new String[numbers.length];

        //int배열 String 배열로 변환
        for(int i=0; i < numbers.length; i++) {
            str[i] = String.valueOf(numbers[i]);
        }

        viewStrArray(str);
        System.out.println();

        //내림차순 정렬
        Arrays.sort(str, new Comparator<String>() {
            @Override
            public int compare(String a, String b) {
                System.out.println();
                viewStrArray(str);
                System.out.println();
                System.out.println(a + " :: " + b);
                System.out.println();

                return (b+a).compareTo(a+b);
            }
        });

        System.out.println();
        viewStrArray(str);
        
        //0값이 중복일경우 ex){0,0,0}
        //답이 000이 나오면 안되므로 첫번째값이 0이면 0을 리턴
        if(str[0].equals("0")){
            return "0";
        }

        for(String s : str) answer += s;
        
        return answer;
    }
}

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 = new StringBuilder();
        for(Integer i : list) {
            sb.append(i);
        }
        answer = sb.toString();
        if(answer.charAt(0) == '0') {
            return "0";
        }else {
            return answer;
        }
    }
}

import java.util.Arrays;
import java.util.Comparator;

class Solution {
    public String solution(int[] numbers) {
        String[] nums = new String[numbers.length];

        for (int i=0; i<nums.length; i++) 
            nums[i] = numbers[i] + "";

        Arrays.sort(nums, new Comparator<String>() {
            public int compare(String o1, String o2) {
                return (o2 + o1).compareTo(o1 + o2);
            }
        });

        String ans = "";
        for (int i=0; i<numbers.length; i++)
            ans += nums[i];

        return ans.charAt(0) == '0' ? "0" : ans;
    }
}