[알고리즘문제풀기] 안전지대

문제

내가 작성한 정답

class Solution {
    public int solution(int[][] board) {
        int answer = 0, len = board.length;
        boolean[][] boom = new boolean[len][len];
        for(int i=0; i<len; i++){
            for(int j=0; j<len; j++){
                if(board[i][j]==1){
                    for(int k = -1; k<2; k++){
                        for(int l= -1;l<2;l++){
                          if(i+k<0 || j+l<0 || i+k>len-1 || j+l>len-1) continue;
                          else boom[i+k][j+l]=true;
                        }
                    }
                }
            }
        }
        for(boolean[] bb:boom){
            for(boolean b: bb){
                if(!b) answer++;
            }
        }
        return answer;
    }
}

다른 사람들의 정답

class Solution {
    public int solution(int[][] board) {
        int answer = 0;
        int length = board.length;   //길이
        int[][] temp = new int[length+2][length+2];
        // 길이를 2 늘린 액자용 배열 생성 -> 이러면 단순한 조건식으로 안전영역 구할 수 있음

        // 액자에 board 이식.
        for(int i=1; i<length+1; i++){
            for(int j=1; j<length+1;j++){
                temp[i][j]=board[i-1][j-1];
            }
        }



        //위험지대 찾기
        for(int i=1; i<length+1; i++){
            for(int j=1; j<length+1;j++){
                if(temp[i][j]==1){
                    for(int a = i-1; a<=i+1; a++){
                        for(int b =j-1; b<=j+1; b++){
                            if(temp[a][b]!=1) temp[a][b]=2;
                        }
                    }
                }
            }
        }

        // 안전지대 카운트
        for(int i=1; i<length+1; i++){
            for(int j=1; j<length+1;j++){
                if(temp[i][j]==0) answer++;
                System.out.print(temp[i][j]);
            }
            System.out.println("");
        }


        return answer;
    }
}


import java.util.Arrays;
import java.util.stream.IntStream;
class Solution {
    @FunctionalInterface
    interface BiConsumer<T> {
        void apply(Integer t1, Integer t2);
    }
    public int solution(int[][] board) {
        int answer;
        int[] move = {-1,0,1};
        int[][] chkBoard = new int[board.length][board.length];

        BiConsumer<Integer> drawChk = (x, y) ->{
            Arrays.stream(move)
                    .filter((i)-> 0<= x+i && x+i < board.length)
                    .forEach(i->Arrays.stream(move)
                            .filter(j-> 0 <= j+y && j+y < board.length)
                            .forEach((j)->chkBoard[x+i][y+j] = 1));
        };

        IntStream.range(0, board.length).forEach(i -> IntStream.range(0, board.length).filter(j->board[i][j] == 1).forEach(j->drawChk.apply(i,j)));

        answer = (int)Arrays.stream(chkBoard).mapToLong(i -> Arrays.stream(i).filter(j -> j == 0).count()).sum();

        System.out.println();

        return answer;
    }
}