java: add «1926. Nearest Exit from Enterance in Maze»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/nearest-exit-from-entrance-in-maze.java

@@ -0,0 +1,53 @@
+import java.util.ArrayDeque;
+
+class Solution {
+  private static final int[][] DIRECTIONS =
+      new int[][] {
+        new int[] {0, 1},
+        new int[] {0, -1},
+        new int[] {1, 0},
+        new int[] {-1, 0},
+      };
+
+  private record Cell(int distance, int y, int x) {
+    public boolean onEdge(int width, int height) {
+      return y == 0 || y == height - 1 || x == 0 || x == width - 1;
+    }
+
+    public boolean inBounds(int width, int height) {
+      return y >= 0 && y < height && x >= 0 && x < width;
+    }
+  }
+
+  public int nearestExit(char[][] maze, int[] entrance) {
+    int width = maze[0].length, height = maze.length;
+
+    var visited = new boolean[height][width];
+
+    var q = new ArrayDeque<Cell>();
+    q.offer(new Cell(0, entrance[0], entrance[1]));
+    visited[entrance[0]][entrance[1]] = true;
+
+    while (!q.isEmpty()) {
+      var c = q.poll();
+
+      if (c.onEdge(width, height) && c.distance() > 0) {
+        return c.distance();
+      }
+
+      for (var d : DIRECTIONS) {
+        int dy = d[0], dx = d[1];
+
+        var n = new Cell(c.distance() + 1, c.y() + dy, c.x() + dx);
+        if (!n.inBounds(width, height) || maze[n.y()][n.x()] != '.' || visited[n.y()][n.x()]) {
+          continue;
+        }
+
+        q.offer(n);
+        visited[n.y()][n.x()] = true;
+      }
+    }
+
+    return -1;
+  }
+}