[BOJ/JAVA] 백준 1012번 : 유기농 배추

 

1012번: 유기농 배추

 

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• 생각

bfs의 전형적인 문제인 것 같다.

반복문을 돌면서 1을 만나면 상, 하, 좌, 우의 값이 1인 index를 check해주면서 bfs를 돌렸다. check가 되지않았던 1을 처음 봤을 땐 count를 1씩 증가시켜 주면서 필요한 배추흰지렁이의 수를 맞춰주었다.

 

 

• 코드

정답 코드 : 1을 발견할때마다 bfs로가서 인접한 1을 check해주며 돔.

 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {

	static int[][] array;
	static boolean[][] check;
	static int[] x = { -1, 1, 0, 0 };
	static int[] y = { 0, 0, -1, 1 };
	static int M;
	static int N;

	public static void main(String args[]) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		int testCase = Integer.parseInt(br.readLine());
		StringBuilder sb = new StringBuilder();

		for (int i = 0; i < testCase; i++) {
			StringTokenizer st = new StringTokenizer(br.readLine());
			M = Integer.parseInt(st.nextToken());
			N = Integer.parseInt(st.nextToken());
			int K = Integer.parseInt(st.nextToken());
			array = new int[M][N];
			check = new boolean[M][N];
			for (int j = 0; j < K; j++) {
				st = new StringTokenizer(br.readLine());
				int x = Integer.parseInt(st.nextToken());
				int y = Integer.parseInt(st.nextToken());
				array[x][y] = 1;
			}

			int count = 0;
			for (int a = 0; a < M; a++) {
				for (int b = 0; b < N; b++) {
					if (!check[a][b] && array[a][b] == 1) {
						count++;
						check[a][b] = true;
						bfs(a, b);
					}
				}
			}
			
			sb.append(count + "\n");
		}
		
		System.out.print(sb);
	}

	private static void bfs(int a, int b) {
		Queue<int[]> queue = new LinkedList<>();
		queue.offer(new int[] { a, b });

		while (!queue.isEmpty()) {
			int location[] = queue.poll();

			for (int direction = 0; direction < 4; direction++) {
				int r = location[0] + x[direction];
				int c = location[1] + y[direction];

				if (r >= 0 && c >= 0 && r < M && c < N) {
					if (array[r][c] == 1 && !check[r][c]) {
						queue.offer(new int[] { r, c });
						check[r][c] = true;
					}
				}
			}
		}
	}

}

 

 

정답 코드 : 3달 뒤 코드이다. stream으로 수를 받아왔다.

 

import java.io.IOException;
import java.io.InputStream;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.Queue;

public class Main {
	static int M, N;
	static int[] x = { -1, 1, 0, 0 };
	static int[] y = { 0, 0, -1, 1 };
	static int[][] array;
	static boolean[][] check;
	static StringBuilder sb;

	public static void main(String[] args) throws Exception {
		SetData();
		System.out.println(sb);
	}
	
	private static void SetData() throws Exception {
		InputReader in = new InputReader(System.in);
		
		sb = new StringBuilder();
		int testCase = in.nextInt();

		for (int i = 0; i < testCase; i++) {
			M = in.nextInt();
			N = in.nextInt();
			int K = in.nextInt();
			array = new int[M][N];
			check = new boolean[M][N];
			
			for (int j = 0; j < K; j++) {
				array[in.nextInt()][in.nextInt()] = 1;
			}

			int count = 0;
			for (int a = 0; a < M; a++) {
				for (int b = 0; b < N; b++) {
					if (!check[a][b] && array[a][b] == 1) {
						count++;
						check[a][b] = true;
						bfs(a, b);
					}
				}
			}
			
			sb.append(count + "\n");
		}
	}
	
	private static void bfs(int a, int b) {
		Queue<int[]> queue = new LinkedList<>();
		queue.offer(new int[] { a, b });

		while (!queue.isEmpty()) {
			int location[] = queue.poll();

			for (int direction = 0; direction < 4; direction++) {
				int r = location[0] + x[direction];
				int c = location[1] + y[direction];

				if (r >= 0 && c >= 0 && r < M && c < N) {
					if (array[r][c] == 1 && !check[r][c]) {
						queue.offer(new int[] { r, c });
						check[r][c] = true;
					}
				}
			}
		}
	}
}
class InputReader {
	private final InputStream stream;
	private final byte[] buf = new byte[8192];
	private int curChar, snumChars;

	public InputReader(InputStream st) {
		this.stream = st;
	}

	public int read() {
		if (snumChars == -1)
			throw new InputMismatchException();
		if (curChar >= snumChars) {
			curChar = 0;
			try {
				snumChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (snumChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public int nextInt() {
		int c = read();
		while (isSpaceChar(c)) {
			c = read();
		}
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public long nextLong() {
		int c = read();
		while (isSpaceChar(c)) {
			c = read();
		}
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		long res = 0;
		do {
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public int[] nextIntArray(int n) {
		int a[] = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = nextInt();
		}
		return a;
	}

	public String nextLine() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuilder res = new StringBuilder();
		do {
			res.appendCodePoint(c);
			c = read();
		} while (!isEndOfLine(c));
		return res.toString();
	}

	public boolean isSpaceChar(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	private boolean isEndOfLine(int c) {
		return c == '\n' || c == '\r' || c == -1;
	}
}