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

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;
  }
}