#2061 - Number of Spaces Cleaning Robot Cleaned

Problem Description

A room is represented by a 0-indexed 2D binary matrix room where a 0 represents an empty space and a 1 represents a space with an object. The top left corner of the room will be empty in all test cases.

A cleaning robot starts at the top left corner of the room and is facing right. The robot will continue heading straight until it reaches the edge of the room or it hits an object, after which it will turn 90 degrees clockwise and repeat this process. The starting space and all spaces that the robot visits are cleaned by it.

Return the number of clean spaces in the room if the robot runs indefinitely.

Solution

/**
 * @param {number[][]} room
 * @return {number}
 */
var numberOfCleanRooms = function(room) {
  const rows = room.length;
  const cols = room[0].length;
  const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
  const visited = new Set();
  const states = new Set();
  let row = 0;
  let col = 0;
  let direction = 0;

  while (true) {
    const state = `${row},${col},${direction}`;
    if (states.has(state)) break;

    states.add(state);
    visited.add(`${row},${col}`);

    const nextRow = row + directions[direction][0];
    const nextCol = col + directions[direction][1];

    if (nextRow < 0 || nextRow >= rows || nextCol < 0
        || nextCol >= cols || room[nextRow][nextCol] === 1) {
      direction = (direction + 1) % 4;
    } else {
      row = nextRow;
      col = nextCol;
    }
  }

  return visited.size;
};