[20250623] BOJ / G1 / 열쇠 / 이강현

lkhyun/202506/23 BOJ G1 열쇠.md

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+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+    static int[] dx = {-1,1,0,0};
+    static int[] dy = {0,0,-1,1};
+
+    public static void main(String[] args) throws IOException {
+        int T = Integer.parseInt(br.readLine());
+        for (int t = 0; t < T; t++) {
+            st = new StringTokenizer(br.readLine());
+            int h = Integer.parseInt(st.nextToken());
+            int w = Integer.parseInt(st.nextToken());
+            char[][] map = new char[h][w];
+
+            for (int i = 0; i < h; i++) {
+                String line = br.readLine();
+                for (int j = 0; j < w; j++) {
+                    map[i][j] = line.charAt(j);
+                }
+            }
+
+            String keyInput = br.readLine();
+            Set<Character> keys = new HashSet<>();
+            if (!keyInput.equals("0")) {
+                for (char c : keyInput.toCharArray()) {
+                    keys.add(c);
+                }
+            }
+
+            int documents = 0;
+            while (true) {
+                Set<Character> prevKeys = new HashSet<>(keys);
+
+                int[] result = BFS(map, h, w, keys);
+                documents = result[0];
+
+                boolean foundNewKey = false;
+                for (char key : keys) {
+                    if (!prevKeys.contains(key)) {
+                        foundNewKey = true;
+                        break;
+                    }
+                }
+
+                if (!foundNewKey) {
+                    break;
+                }
+            }
+            bw.write(documents + "\n");
+        }
+        bw.close();
+    }
+
+    static int[] BFS(char[][] map, int h, int w, Set<Character> keys) {
+        ArrayDeque<int[]> q = new ArrayDeque<>();
+        boolean[][] visited = new boolean[h][w];
+        int documents = 0;
+
+        for (int i = 0; i < h; i++) {
+            for (int j = 0; j < w; j++) {
+                if ((i == 0 || i == h-1 || j == 0 || j == w-1) && map[i][j] != '*') {
+                    if (canMove(map[i][j], keys)) {
+                        visited[i][j] = true;
+                        q.offer(new int[]{i, j});
+
+                        if (map[i][j] == '$') {
+                            documents++;
+                        } else if (isLowerCase(map[i][j])) {
+                            keys.add(map[i][j]);
+                        }
+                    }
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int[] curr = q.poll();
+            int x = curr[0], y = curr[1];
+
+            for (int d = 0; d < 4; d++) {
+                int nx = x + dx[d];
+                int ny = y + dy[d];
+
+                if (nx < 0 || nx >= h || ny < 0 || ny >= w || visited[nx][ny]) {
+                    continue;
+                }
+
+                char cell = map[nx][ny];
+
+                if (canMove(cell, keys)) {
+                    visited[nx][ny] = true;
+                    q.offer(new int[]{nx, ny});
+
+                    if (cell == '$') {
+                        documents++;
+                    } else if (isLowerCase(cell)) {
+                        keys.add(cell);
+                    }
+                }
+            }
+        }
+
+        return new int[]{documents};
+    }
+
+    static boolean canMove(char cell, Set<Character> keys) {
+        if (cell == '*') return false;
+        if (cell == '.' || cell == '$') return true;
+        if (isLowerCase(cell)) return true;
+        if (isUpperCase(cell)) {
+            return keys.contains(Character.toLowerCase(cell));
+        }
+        return false;
+    }
+
+    static boolean isUpperCase(char c) {
+        return c >= 'A' && c <= 'Z';
+    }
+
+    static boolean isLowerCase(char c) {
+        return c >= 'a' && c <= 'z';
+    }
+}
+```