Solution.ts

/**
 * class Robot {
 *      // Returns true if the cell in front is open and robot moves into the cell.
 *      // Returns false if the cell in front is blocked and robot stays in the current cell.
 * 		move(): boolean {}
 *
 *      // Robot will stay in the same cell after calling turnLeft/turnRight.
 *      // Each turn will be 90 degrees.
 * 		turnRight() {}
 *
 *      // Robot will stay in the same cell after calling turnLeft/turnRight.
 *      // Each turn will be 90 degrees.
 * 		turnLeft() {}
 *
 * 		// Clean the current cell.
 * 		clean(): {}
 * }
 */

function cleanRoom(robot: Robot) {
    const dirs = [-1, 0, 1, 0, -1];
    const vis = new Set<string>();
    const dfs = (i: number, j: number, d: number) => {
        vis.add(`${i}-${j}`);
        robot.clean();
        for (let k = 0; k < 4; ++k) {
            const nd = (d + k) % 4;
            const [x, y] = [i + dirs[nd], j + dirs[nd + 1]];
            if (!vis.has(`${x}-${y}`) && robot.move()) {
                dfs(x, y, nd);
                robot.turnRight();
                robot.turnRight();
                robot.move();
                robot.turnRight();
                robot.turnRight();
            }
            robot.turnRight();
        }
    };
    dfs(0, 0, 0);
}