[20250913] PGM / LV2 / 리코쳇 로봇 / 김수연

suyeun84/202509/13 PGM LV2 리코쳇 로봇.md

@@ -0,0 +1,68 @@
+```java
+import java.util.*;
+class Solution {
+    static int[][] dir = new int[][]{{1,0}, {-1,0}, {0,1}, {0,-1}};
+    static int answer = -1;
+    static Point start, target;
+    static int N, M;
+    static char[][] map;
+    static int[][] visited;
+
+    public int solution(String[] board) {
+        N = board.length;
+        M = board[0].length();
+        map = new char[N][M];
+        visited = new int[N][M];
+        for (int i = 0; i < N; i++) {
+            map[i] = board[i].toCharArray();
+            Arrays.fill(visited[i], Integer.MAX_VALUE);
+            for (int j = 0; j < M; j++) {
+                if (map[i][j] == 'R') start = new Point(i, j, 0);
+                else if (map[i][j] == 'G') target = new Point(i, j, 0);
+            }
+        }
+
+        bfs();
+
+        return answer;
+    }
+
+    private void bfs() {
+        Queue<Point> q = new LinkedList<>();
+        q.add(new Point(start.y, start.x, start.cnt));
+        visited[start.y][start.x] = 0;
+        while (!q.isEmpty()) {
+            Point curr = q.poll();
+            if (curr.y == target.y && curr.x == target.x) {
+                answer = curr.cnt;
+                return;
+            }
+
+            for (int[] d : dir) {
+                int ny = curr.y, nx = curr.x;
+                while (true) {
+                    ny += d[0];
+                    nx += d[1];
+                    if (ny < 0 || ny >= N || nx < 0 || nx >= M || map[ny][nx] == 'D') {
+                        ny -= d[0];
+                        nx -= d[1];
+                        if (visited[ny][nx] <= curr.cnt+1) break;
+                        q.add(new Point(ny, nx, curr.cnt+1));
+                        visited[ny][nx] = curr.cnt+1;
+                    }
+                }
+            }
+        }
+
+    }
+
+    class Point {
+        int y, x, cnt;
+        public Point(int y, int x, int cnt) {
+            this.y = y;
+            this.x = x;
+            this.cnt = cnt;
+        }
+    }
+}
+```