Merge pull request #1004 from AlgorithmWithGod/LiiNi-coder

[20250929] BOJ / G5 / 십자뒤집기 / 이인희

Author: ShinHeeEul

LiiNi-coder/202509/29 BOJ 십자뒤집기.md

@@ -0,0 +1,74 @@
+```java
+import java.io.*;
+import java.util.*;
+import java.util.stream.IntStream;
+
+public class Main {
+    private static int N = 3;
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int T = Integer.parseInt(br.readLine());
+        while(T-- > 0){
+            var map = 0;
+            for(int r = 0; r < N; r++) {
+                char[] cs = br.readLine().toCharArray();
+                for (int c = 0; c < N; c++) {
+                    if (cs[c] == '*')
+                        map += 1<<(N*r + c);
+                }
+            }
+            System.out.println(solve(map));
+        }
+        br.close();
+    }
+
+    private static int solve(int initialMap) {
+        boolean[] visited = new boolean[512];
+        Deque<int[]> q = new ArrayDeque<>();
+        q.add(new int[]{initialMap, 0});
+        visited[initialMap] = true;
+        while(!q.isEmpty()){
+            int[] temp = q.poll();
+            int map = temp[0], count = temp[1];
+            if(map == 0){
+                return count;
+            }
+            for(int di: IntStream.range(0, 9).toArray()){
+                int nextMap = toggle(map, di);
+                if(visited[nextMap]) continue;
+                visited[nextMap] = true;
+                q.add(new int[]{nextMap, count+1});
+            }
+        }
+        return -1;
+    }
+
+    private static int toggle(int map, int black1d) {
+        List<Integer> masks = new ArrayList<>();
+        masks.add(black1d);
+        if(black1d % N == 0){
+            masks.add(black1d + 1);
+        }else if(black1d % N == 1){
+            masks.add(black1d + 1);
+            masks.add(black1d-1);
+        }else{
+            masks.add(black1d-1);
+        }
+
+        if(black1d / N == 0){
+            masks.add(black1d + N);
+        }else if(black1d / N == 1){
+            masks.add(black1d - N);
+            masks.add(black1d + N);
+        }else{
+            masks.add(black1d-N);
+        }
+
+        for(int mask: masks){
+            map ^= 1<<mask;
+        }
+        return map;
+    }
+}
+
+```