[알고리즘] 순환(Recursion) 05 - Counting Cells in a Blob

순환(Recursion) 응용편 : Counting Cells in a Blob

인프론 강의를 보면서 연습하고 기록하고 있습니다

의사코드

Algorithm for countCells(x, y) {
	if the pixel(x, y) is outside the grid
		the result is 0;
	else if pixel(x, y) is not an image picel or already counted
		the result is 0;
	else
		set the colour of the pixel(x, y) to a red colour;
		the result is 1 plus the nuber of cells in each piece of
			the blob that includes a nearest neighbour;
}

Java코드

private static int N = 8; //범위
private static int[][] grid = {
		{1, 0, 0, 0, 0, 0, 0, 1},
		{0, 1, 1, 0, 0, 1, 0, 0},
		{1, 1, 0, 0, 1, 0, 1, 0},
		{0, 0, 0, 0, 0, 1, 0, 0},
		{0, 1, 0, 1, 0, 1, 0, 0},
		{0, 1, 0, 1, 0, 1, 0, 0},
		{1, 0, 0, 0, 1, 0, 0, 1},
		{0, 1, 1, 0, 0, 1, 1, 1}
};

private static final int BACKGROUND = 0;
private static final int IMAGE = 1;
private static final int ALREADY_COUNTED = 2;

public static void main(String[] args) {
	printImage();
	System.out.println("blob size : "+countCells(3,5));
	printImage();
}

public static int countCells (int x, int y) {
	if (x<0 || y<0 || x>=N || y>=N) { //범위 넘어갔는지 체크
		return 0;
	}else if(grid[x][y] != IMAGE){ //이미지 컬러가 아닐 때
		return 0;
	}else {
		grid[x][y] = ALREADY_COUNTED;
		return 1
				+ countCells(x-1, y) + countCells(x-1, y+1)
				+ countCells(x, y+1) + countCells(x+1, y+1)
				+ countCells(x+1, y) + countCells(x+1, y-1)
				+ countCells(x, y-1) + countCells(x-1, y-1);
	}
}

public static void printImage() {
	System.out.println("---------------------------------");
	for (int i = 0; i < grid.length; i++) {
		for (int j = 0; j < grid.length; j++) {
			System.out.print(grid[i][j] +" ");
		}
		System.out.println();
	}
	System.out.println("---------------------------------");
}

---------------------------------
1 0 0 0 0 0 0 1
0 1 1 0 0 1 0 0
1 1 0 0 1 0 1 0
0 0 0 0 0 1 0 0
0 1 0 1 0 1 0 0
0 1 0 1 0 1 0 0
1 0 0 0 1 0 0 1
0 1 1 0 0 1 1 1
---------------------------------
blob size : 13
---------------------------------
1 0 0 0 0 0 0 1
0 1 1 0 0 2 0 0
1 1 0 0 2 0 2 0
0 0 0 0 0 2 0 0
0 1 0 2 0 2 0 0
0 1 0 2 0 2 0 0
1 0 0 0 2 0 0 2
0 1 1 0 0 2 2 2
---------------------------------