[알고리즘문제풀기] 2의 영역

문제

내가 작성한 정답

import java.util.*;
import java.util.stream.*;
class Solution {
    public int[] solution(int[] arr) {
        int first = Arrays.stream(arr).boxed().collect(Collectors.toList()).indexOf(2);
        int next =  -1;
        for(int i= arr.length-1; i > first; i--){
            if(arr[i]==2){
                next = i; break;
            }
        }
        return (first==-1)? new int[]{-1}
                : (next==-1)? new int[]{2}
                : Arrays.copyOfRange(arr,first,next+1);
    }
}

import java.util.Arrays;
class Solution {
    public int[] solution(int[] arr) {
        int first = -1, last = -1;
        for(int i=0; i< arr.length; i++){
            if(arr[i]==2){
                if(first==-1){
                    first = i;
                }
                last = i;
            }
        }
        return (first==-1)? new int[]{-1}
                : (last==-1)? new int[]{2}
                : Arrays.copyOfRange(arr,first,last+1);
    }
}

다른 사람들의 정답

import java.util.stream.IntStream;

class Solution {
    public int[] solution(int[] arr) {
        int[] idx = IntStream.range(0, arr.length).filter(i -> arr[i] == 2).toArray();
        if (idx.length == 0) return new int[]{-1};
        return IntStream.rangeClosed(idx[0], idx[idx.length - 1]).map(i -> arr[i]).toArray();
    }
}


import java.util.*;
class Solution {
    public ArrayList<Integer> solution(int[] arr) {
        ArrayList<Integer> answer = new ArrayList<Integer>();
        int start = -1;
        int end = -1;
        for(int i = 0; i<arr.length; i++){
            if(arr[i]==2){
                start = i;
                break;
            }
        }
        for(int i = arr.length-1; i>=0; i--){
            if(arr[i]==2){
                end = i;
                break;
            }
        }
        if(start==-1 && end==-1){
            answer.add(-1);
        } else{
            for(int i = start; i<=end; i++){
                answer.add(arr[i]);
            }
        }

        return answer;
    }
}