[20250418] BOJ / P5 / 백조의 호수 / 이강현

Author: lkhyun

lkhyun/202504/18 BOJ P5 백조의 호수.md

@@ -0,0 +1,111 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static int r, c, starti = -1, startj = -1, endi, endj;
+    static char[][] matrix;
+    static boolean[][] check;
+    static boolean[][] watercheck;
+    static ArrayDeque<int[]> wq, sq;
+    static int[] di = {-1, 1, 0, 0};
+    static int[] dj = {0, 0, -1, 1};
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        r = Integer.parseInt(st.nextToken());
+        c = Integer.parseInt(st.nextToken());
+        matrix = new char[r][c];
+        check = new boolean[r][c];
+        watercheck = new boolean[r][c];
+        wq = new ArrayDeque<>();
+        sq = new ArrayDeque<>();
+
+        for (int i = 0; i < r; i++) {
+            String line = br.readLine();
+            for (int j = 0; j < c; j++) {
+                matrix[i][j] = line.charAt(j);
+                if (matrix[i][j] == 'L') {
+                    if (starti == -1 && startj == -1) {
+                        starti = i;
+                        startj = j;
+                    } else {
+                        endi = i;
+                        endj = j;
+                    }
+                    matrix[i][j] = '.';
+                }
+
+                if (matrix[i][j] == '.') {
+                    wq.add(new int[] {i, j});
+                    watercheck[i][j] = true;
+                }
+            }
+        }
+
+        sq.add(new int[] {starti, startj});
+        check[starti][startj] = true;
+
+        int time = 0;
+        while (!move()) {
+            melting();
+            time++;
+        }
+        bw.write(time + "");
+        bw.close();
+    }
+
+    public static boolean move() {
+        ArrayDeque<int[]> q = new ArrayDeque<>();
+
+        while (!sq.isEmpty()) {
+            int[] cur = sq.poll();
+            if (cur[0] == endi && cur[1] == endj) {
+                return true;
+            }
+
+            for (int k = 0; k < 4; k++) {
+                int newi = cur[0] + di[k];
+                int newj = cur[1] + dj[k];
+
+                if (newi < 0 || newi >= r || newj < 0 || newj >= c || check[newi][newj])
+                    continue;
+
+                check[newi][newj] = true;
+                if (matrix[newi][newj] == '.') {
+                    sq.add(new int[] {newi, newj});
+                } else if (matrix[newi][newj] == 'X') {
+                    q.add(new int[] {newi, newj});
+                }
+            }
+        }
+
+        sq = q;
+        return false;
+    }
+
+    public static void melting() {
+        int size = wq.size();
+        for (int i = 0; i < size; i++) {
+            int[] cur = wq.poll();
+
+            for (int k = 0; k < 4; k++) {
+                int newi = cur[0] + di[k];
+                int newj = cur[1] + dj[k];
+
+                if (newi < 0 || newi >= r || newj < 0 || newj >= c || watercheck[newi][newj])
+                    continue;
+                if (matrix[newi][newj] == 'X') {
+                    matrix[newi][newj] = '.';
+                    wq.add(new int[] {newi, newj});
+                    watercheck[newi][newj] = true;
+                }
+            }
+        }
+    }
+}
+
+```