[20250428] BOJ / G4 / DSLR / 이강현

lkhyun/202504/28 BOJ G4 DSLR.md

@@ -0,0 +1,78 @@
+```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));
+
+    public static void main(String[] args) throws Exception {
+        int T = Integer.parseInt(br.readLine());
+        while (T-- > 0) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int A = Integer.parseInt(st.nextToken());
+            int B = Integer.parseInt(st.nextToken());
+            bfs(A, B);
+        }
+        bw.flush();
+        bw.close();
+    }
+
+    static void bfs(int start, int target) throws IOException {
+        boolean[] visited = new boolean[10000];
+        int[] prev = new int[10000];
+        char[] op = new char[10000];
+
+        ArrayDeque<Integer> q = new ArrayDeque<>();
+        visited[start] = true;
+        q.add(start);
+
+        while (!q.isEmpty()) {
+            int cur = q.poll();
+            if (cur == target) break;
+
+            // D
+            int next = (cur * 2) % 10000;
+            if (!visited[next]) {
+                visited[next] = true;
+                prev[next] = cur;
+                op[next] = 'D';
+                q.add(next);
+            }
+            // S
+            next = (cur == 0 ? 9999 : cur - 1);
+            if (!visited[next]) {
+                visited[next] = true;
+                prev[next] = cur;
+                op[next] = 'S';
+                q.add(next);
+            }
+            // L
+            next = (cur % 1000) * 10 + cur / 1000;
+            if (!visited[next]) {
+                visited[next] = true;
+                prev[next] = cur;
+                op[next] = 'L';
+                q.add(next);
+            }
+            // R
+            next = (cur % 10) * 1000 + cur / 10;
+            if (!visited[next]) {
+                visited[next] = true;
+                prev[next] = cur;
+                op[next] = 'R';
+                q.add(next);
+            }
+        }
+
+        StringBuilder sb = new StringBuilder();
+        for (int p = target; p != start; p = prev[p]) {
+            sb.append(op[p]);
+        }
+        bw.write(sb.reverse().toString());
+        bw.write('\n');
+    }
+}
+
+
+```