LeetCode 489. Robot Room Cleaner

/**
 * // This is the robot‘s control interface.
 * // You should not implement it, or speculate about its implementation
 * class Robot {
 *   public:
 *     // 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.
 *     bool move();
 *
 *     // Robot will stay in the same cell after calling turnLeft/turnRight.
 *     // Each turn will be 90 degrees.
 *     void turnLeft();
 *     void turnRight();
 *
 *     // Clean the current cell.
 *     void clean();
 * };
 */
class Solution {
public:
    vector<vector<int>> dirs={{-1,0},{0,1},{1,0},{0,-1}}; // up right down left
    unordered_map<int,unordered_map<int,bool>> visited; // visited[x][y]
    
    void cleanRoom(Robot& robot) {
        dfs(robot,0,0,0);
    }
    
    void dfs(Robot &robot, int i, int j, int dir){
        if (visited[i][j]) return;
        //cout << x << ‘ ‘ << y << endl;
        robot.clean(); visited[i][j]=true;
        
        for (int k=0;k<4;++k){
            if (robot.move()){
                dfs(robot,i+dirs[dir][0],j+dirs[dir][1],dir);
                robot.turnRight();
                robot.turnRight();
                robot.move();
                robot.turnRight();
                robot.turnRight();
            }
            robot.turnRight();
            dir = (dir+1)%4;
        }
    }
};