[20250925] PGM / LV2 / 리코챗 로봇 / 이인희

Author: LiiNi-coder

LiiNi-coder/202509/25 PGM 리코챗 로봇.md

@@ -0,0 +1,73 @@
+```java
+import java.util.*;
+
+class Solution {
+    int[] Dr = {-1, 1, 0, 0};
+    int[] Dc = {0, 0, -1, 1};
+    int Rr, Rc, Gr, Gc;
+    int H;
+    int W;
+    boolean[][] visited;
+
+    public int solution(String[] board) {
+
+        H = board.length;
+        W = board[0].length();
+        visited = new boolean[H][W];
+
+        for (int i = 0; i < H; i++) {
+            for (int j = 0; j < W; j++) {
+                char c = board[i].charAt(j);
+                if (c == 'R') {
+                    Rr = i;
+                    Rc = j;
+                }
+                if (c == 'G') {
+                    Gr = i;
+                    Gc = j;
+                }
+            }
+        }
+        Queue<int[]> q = new ArrayDeque<>();
+        q.add(new int[]{Rr, Rc, 0});
+        visited[Rr][Rc] = true;
+
+        while (!q.isEmpty()) {
+            int[] cur = q.poll();
+            int r = cur[0];
+            int c = cur[1];
+            int d = cur[2];
+            if (r == Gr && c == Gc) {
+                return d;
+            }
+            for (int i = 0; i < 4; i++) {
+                int[] next = slide(r, c, i, board);
+                int nr = next[0], nc = next[1];
+                if (visited[nr][nc])
+                    continue;
+                
+                visited[nr][nc] = true;
+                q.add(new int[]{nr, nc, d + 1});
+            }
+        }
+        
+        return -1;
+    }
+
+    int[] slide(int r, int c, int direction, String[] board) {
+        int nr = r, nc = c;
+        while (true) {
+            int tr = nr + Dr[direction];
+            int tc = nc + Dc[direction];
+            if (tr < 0 || tr >= H || tc < 0 || tc >= W)
+                break;
+            if (board[tr].charAt(tc) == 'D')
+                break;
+            nr = tr;
+            nc = tc;
+        }
+        return new int[]{nr, nc};
+    }
+}
+
+```