# Scott@JAVA

Java, 一杯浓浓的咖啡伴你到深夜

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)

public class DrawLines {

// current cursor position
private int xPos, yPos;

private int direction;

private char[][] canvas;

public DrawLines() {
xPos
= 0;
yPos
= 0;

// initial drawing direction downwards
direction = 270;
canvas
= new char[20][20];
}

private void initCanvas() {

for (int i = 0; i < 20; i++)

for (int j = 0; j < 20; j++)
canvas[i][j]
= '.';
}

public String[] excute(String[] commands) {
initCanvas();

for (int i = 0; i < commands.length; i++{

if (commands[i].equals("LEFT")) {

// when come cross "LEFT", turn 90 degrees couter-clockwise
direction += 90;

if (direction == 360)
direction
= 0;
}
else {

int len = Integer.parseInt(commands[i].split(" ")[1]);

switch (direction) {

case 0:

// draw from left to right
for (int j = 0; j <= len; j++)
canvas[xPos][yPos
++= 'X';
yPos
--;

break;

case 90:

// draw from down to up
for (int j = 0; j <= len; j++)
canvas[xPos
--][yPos] = 'X';
xPos
++;

break;

case 180:

// draw from right to left
for (int j = 0; j <= len; j++)
canvas[xPos][yPos
--= 'X';
yPos
++;

break;

case 270:

// draw from up to down
for (int j = 0; j <= len; j++)
canvas[xPos
++][yPos] = 'X';
xPos
--;

break;
}

}

}

String[] s
= new String[20];

for (int i = 0; i < 20; i++)
s[i]
= new String(canvas[i]);

return s;
}

public static void main(String[] args) {
String[] cmds
= "LEFT""FORWARD 19""LEFT""LEFT""LEFT",

"FORWARD 18""LEFT""LEFT""LEFT""FORWARD 17""LEFT",

"LEFT""LEFT""FORWARD 16""LEFT""LEFT""LEFT",

"FORWARD 15""LEFT""LEFT""LEFT""FORWARD 14""LEFT",

"LEFT""LEFT""FORWARD 13""LEFT""LEFT""LEFT",

"FORWARD 12""LEFT""LEFT""LEFT""FORWARD 11""LEFT",

"LEFT""LEFT""FORWARD 10""LEFT""LEFT""LEFT",

"FORWARD 9""LEFT""LEFT""LEFT""FORWARD 8""LEFT",

"LEFT""LEFT""FORWARD 7" }
;
DrawLines drawLines
= new DrawLines();
String[] s
= drawLines.excute(cmds);

for (int i = 0; i < 20; i++)
System.out.println(s[i]);
}

}

posted on 2005-12-01 11:49 Scott@JAVA 阅读(381) 评论(0)  编辑  收藏 所属分类: My Java App

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