GOOGLE挑战赛练习题1及答案(200分)

Problem Statement

A simple line drawing program uses a blank 20 x 20 pixel canvas and a directional cursor that starts at the upper left corner pointing straight down. The upper left corner of the canvas is at (0, 0) and the lower right corner is at (19, 19). You are given a String[], commands, each element of which contains one of two possible commands. A command of the form "FORWARD x" means that the cursor should move forward by x pixels. Each pixel on its path, including the start and end points, is painted black. The only other command is "LEFT", which means that the cursor should change its direction by 90 degrees counterclockwise. So, if the cursor is initially pointing straight down and it receives a single "LEFT" command, it will end up pointing straight to the right. Execute all the commands in order and return the resulting 20 x 20 pixel canvas as a String[] where character j of element i represents the pixel at (i, j). Black pixels should be represented as uppercase 'X' characters and blank pixels should be represented as '.' characters.

Definition

Class:	DrawLines
Method:	execute
Parameters:	String[]
Returns:	String[]
Method signature:	String[] execute(String[] commands)
(be sure your method is public)

 

  1public class DrawLines
  2{
  3  class Pos
  4  {
  5    private int X;
  6    private int Y;
  7    private String status = ".";
  8
  9    public Pos(int x,int y)
 10    {
 11      this.X = x;
 12      this.Y = y;
 13      this.status = ".";
 14    }
 15
 16    public int getX()
 17    {
 18      return X;
 19    }
 20
 21    public int getY()
 22    {
 23      return Y;
 24    }
 25
 26    public void setX(int x)
 27    {
 28      this.X = x;
 29    }
 30
 31    public void setY(int y)
 32    {
 33      this.Y = y;
 34    }
 35
 36    public void setStatus(String s)
 37    {
 38      this.status = s;
 39    }
 40
 41    public String getSatus()
 42    {
 43      return status;
 44    }
 45
 46    public void showPos()
 47    {
 48      String xStr=X+"";
 49      String yStr=Y+"";
 50
 51      if(X<10)
 52      {
 53        xStr = "0"+xStr;
 54      }
 55
 56      if(Y<10)
 57      {
 58        yStr = "0"+yStr;
 59      }
 60    }
 61  }
 62
 63  public int min = 0, max = 19;
 64  public int North = 1, South = 3, West = 2, East = 0;
 65  public String LEFT = "LEFT", FORWARD = "FORWARD";
 66  public Pos[][] map = null;
 67
 68
 69
 70  public DrawLines()
 71 {
 72   this.direction = South;
 73   pos = new Pos(0,0);
 74
 75   //走之前初始化地图.
 76   map = new Pos[max + 1][max + 1];
 77   for(int row = 0;row<=max;row++)
 78   {
 79     for(int col=0;col<=max;col++)
 80     {
 81       map[row][col] = new Pos(row,col);
 82     }
 83   }
 84 }
 85
 86  public void showMap()
 87  {for (int col = 0; col <= max; col++)
 88
 89    {
 90      for (int row = 0; row <= max; row++)
 91      {
 92        System.out.print(map[row][col].getSatus());
 93      }
 94      System.out.println(); 
 95    }
 96  }
 97
 98  private Pos pos = null;
 99  private int direction = South;
100
101  public Pos getPos()
102  {
103    return pos;
104  }
105  public void setPos(Pos pos)
106  {
107    this.pos = pos;
108  }
109  /** *//**
110   *
111   * @param cmd
112   */
113  public void execute(String cmd)
114  {
115    if (cmd.equals("LEFT"))
116    {
117      Left();
118    }
119    else if (cmd.indexOf(FORWARD) >= 0)
120    {
121      int from = cmd.indexOf(FORWARD);
122      String stepStr = cmd.substring(from + FORWARD.length());
123      stepStr = stepStr.trim();
124      int step = Integer.parseInt(stepStr);
125      forward(step);
126    }
127    else
128