钻头操作 - 到底发生了什么？
https://stackoverflow.com/questions/4632101
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08-10-2019 - |
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我有以下JavaScript脚本来生成2D迷宫：
/*
* 3 June 2003, [[:en:User:Cyp]]:
* Maze, generated by my algorithm
* 24 October 2006, [[:en:User:quin]]:
* Source edited for clarity
* 25 January 2009, [[:en:User:DebateG]]:
* Source edited again for clarity and reusability
* 1 June 2009, [[:en:User:Nandhp]]:
* Source edited to produce SVG file when run from the command-line
* 7 January, 2011 [[:en:User:SharkD]]:
* Source converted to JavaScript
*
* This program was originally written by [[:en:User:Cyp]], who
* attached it to the image description page for an image generated by
* it on en.wikipedia. The image was licensed under CC-BY-SA-3.0/GFDL.
*/
/* Recreate a math function that exists in Java but not JavaScript. */
Math.nextInt = function (number) {
return Math.floor(Math.random() * number)
}
/* Recreate a system function that exists in Java but not JavaScript.
* Uncomment either WScript.Echo() or alert() depending on whether you are
* running the script from the Windows command-line or a Web page.
*/
function println(string)
{
// if inside Windows Scripting Host
WScript.Echo(string)
// if inside a Web page
// alert(string)
}
/* Define the bit masks */
var Constants =
{
WALL_ABOVE : 1,
WALL_BELOW : 2,
WALL_LEFT : 4,
WALL_RIGHT : 8,
QUEUED : 16,
IN_MAZE : 32
}
/* Construct a Maze with specified width, height, and cell_width */
function Maze(width, height, cell_width) {
if (width)
this.width = width;
else
this.width = 20;
if (height)
this.height = height;
else
this.height = 20;
if (cell_width)
this.cell_width = cell_width;
else
this.cell_width = 10;
this.maze = []
/* The maze generation algorithm. */
this.createMaze = function() {
var width = this.width
var height = this.height
var maze = this.maze
var x, y, n, d;
var dx = [ 0, 0, -1, 1 ];
var dy = [ -1, 1, 0, 0 ];
var todo = new Array(height * width);
var todonum = 0;
/* We want to create a maze on a grid. */
/* We start with a grid full of walls. */
for (x = 0; x < width; ++x) {
maze[x] = []
for (y = 0; y < height; ++y) {
if (x == 0 || x == width - 1 || y == 0 || y == height - 1) {
maze[x][y] = Constants.IN_MAZE;
}
else {
maze[x][y] = 63;
}
}
}
/* Select any square of the grid, to start with. */
x = 1 + Math.nextInt(width - 2);
y = 1 + Math.nextInt(height - 2);
/* Mark this square as connected to the maze. */
maze[x][y] &= ~48;
/* Remember the surrounding squares, as we will */
for (d = 0; d < 4; ++d) {
if ((maze[x + dx[d]][y + dy[d]] & Constants.QUEUED) != 0) {
/* want to connect them to the maze. */
todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]);
maze[x + dx[d]][y + dy[d]] &= ~Constants.QUEUED;
}
}
/* We won't be finished until all is connected. */
while (todonum > 0) {
/* We select one of the squares next to the maze. */
n = Math.nextInt(todonum);
x = todo[n] >> 16; /* the top 2 bytes of the data */
y = todo[n] & 65535; /* the bottom 2 bytes of the data */
/* We will connect it, so remove it from the queue. */
todo[n] = todo[--todonum];
/* Select a direction, which leads to the maze. */
do {
d = Math.nextInt(4);
}
while ((maze[x + dx[d]][y + dy[d]] & Constants.IN_MAZE) != 0);
/* Connect this square to the maze. */
maze[x][y] &= ~((1 << d) | Constants.IN_MAZE);
maze[x + dx[d]][y + dy[d]] &= ~(1 << (d ^ 1));
/* Remember the surrounding squares, which aren't */
for (d = 0; d < 4; ++d) {
if ((maze[x + dx[d]][y + dy[d]] & Constants.QUEUED) != 0) {
/* connected to the maze, and aren't yet queued to be. */
todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]);
maze[x + dx[d]][y + dy[d]] &= ~Constants.QUEUED;
}
}
/* Repeat until finished. */
}
/* Add an entrance and exit. */
maze[1][1] &= ~Constants.WALL_ABOVE;
maze[width - 2][height - 2] &= ~Constants.WALL_BELOW;
}
/* Called to write the maze to an SVG file. */
this.printSVG = function () {
println("<svg width=\"" + (width * cell_width) + "\" height=\"" + (height*cell_width) + "\" version=\"1.1\" xmlns=\"http://www.w3.org/2000/svg\">\n"
+ " <g stroke=\"black\" stroke-width=\"1\" stroke-linecap=\"round\">\n" + this.drawMaze() + " </g>\n</svg>\n");
}
/* Main maze-drawing loop. */
this.drawMaze = function () {
var x, y;
var width = this.width;
var height = this.height;
var cell_width = this.cell_width
var outstring = ""
for (x = 1; x < width - 1; ++x) {
for (y = 1; y < height - 1; ++y) {
if ((this.maze[x][y] & Constants.WALL_ABOVE) != 0)
outstring += this.drawLine(x * cell_width, y * cell_width, (x + 1) * cell_width, y * cell_width);
if ((this.maze[x][y] & Constants.WALL_BELOW) != 0)
outstring += this.drawLine(x * cell_width, (y + 1) * cell_width, (x + 1) * cell_width, (y + 1) * cell_width);
if ((this.maze[x][y] & Constants.WALL_LEFT) != 0)
outstring += this.drawLine(x * cell_width, y * cell_width, x * cell_width, (y + 1) * cell_width);
if ((this.maze[x][y] & Constants.WALL_RIGHT) != 0)
outstring += this.drawLine((x + 1) * cell_width, y * cell_width, (x + 1) * cell_width, (y + 1) * cell_width);
}
}
return outstring
}
/* Draw a line, either in the SVG file or on the screen. */
this.drawLine = function (x1, y1, x2, y2) {
return " <line x1=\"" + x1 + "\" y1=\"" + y1 + "\" x2=\"" + x2 + "\" y2=\"" + y2 + "\" />\n";
}
}
/* Initialization method that will be called when the program is
* run from the command-line. Maze will be written as SVG file. */
function main(args) {
var m = new Maze();
m.createMaze();
m.printSVG();
}
/* execute the program */
main()
我想扩展脚本，使其创建一个六轴3D迷宫。但是，为了做到这一点，我必须了解位操作以及它们的使用方式。有人可以向我解释为什么原始作者选择使用位操作，以及他们在脚本中所做的事情吗？
谢谢！
编辑 - 结论]由于现在解决了该问题，仅供参考，这是脚本的3D版本：
/*
* 3 June 2003, [[:en:User:Cyp]]:
* Maze, generated by my algorithm
* 24 October 2006, [[:en:User:quin]]:
* Source edited for clarity
* 25 January 2009, [[:en:User:DebateG]]:
* Source edited again for clarity and reusability
* 1 June 2009, [[:en:User:Nandhp]]:
* Source edited to produce SVG file when run from the command-line
* 7 January, 2011 [[:en:User:SharkD]]:
* Source converted to JavaScript and third axis added
*
* This program was originally written by [[:en:User:Cyp]], who
* attached it to the image description page for an image generated by
* it on en.wikipedia. The image was licensed under CC-BY-SA-3.0/GFDL.
*/
/* Recreate a math function that exists in Java but not JavaScript. */
Math.nextInt = function (number) {
return Math.floor(Math.random() * number)
}
/* Recreate a system function that exists in Java but not JavaScript.
* Uncomment either WScript.Echo() or alert() depending on whether you are
* running the script from the Windows command-line or a Web page.
*/
function println(string)
{
// if inside Windows Scripting Host
WScript.Echo(string)
// if inside a Web page
// alert(string)
}
/* Define the bit masks */
var WALL_ABOVE = 1;
var WALL_BELOW = 2;
var WALL_LEFT = 4;
var WALL_RIGHT = 8;
var WALL_FRONT = 16;
var WALL_BACK = 32;
var QUEUED = 64;
var IN_MAZE = 128;
/* Construct a Maze with specified lenx, leny, and cell_width */
function Maze(lenx, leny, lenz, cell_width) {
if (lenx)
this.lenx = lenx;
else
this.lenx = 20;
if (leny)
this.leny = leny;
else
this.leny = 20;
if (lenz)
this.lenz = lenz;
else
this.lenz = 8;
if (cell_width)
this.cell_width = cell_width;
else
this.cell_width = 10;
this.maze = []
/* The maze generation algorithm. */
this.createMaze = function() {
var lenx = this.lenx
var leny = this.leny
var lenz = this.lenz
var maze = this.maze
var x, y, z, n, d;
var dx = [ 0, 0, -1, 1, 0, 0 ];
var dy = [ -1, 1, 0, 0, 0, 0 ];
var dz = [ 0, 0, 0, 0, -1, 1 ];
var todo = new Array(leny * lenx * lenz);
var todonum = 0;
/* We want to create a maze on a grid. */
/* We start with a grid full of walls. */
/* Except for the outer walls which are left open? */
for (x = 0; x < lenx; ++x) {
maze[x] = []
for (y = 0; y < leny; ++y) {
maze[x][y] = []
for (z = 0; z < lenz; ++z)
{
if (x == 0 || x == lenx - 1 || y == 0 || y == leny - 1 || z == 0 || z == lenz - 1) {
maze[x][y][z] = IN_MAZE;
}
else {
maze[x][y][z] = WALL_ABOVE + WALL_BELOW + WALL_LEFT + WALL_RIGHT + WALL_FRONT + WALL_BACK + QUEUED + IN_MAZE; // DUNNO!!!! 255
}
}
}
}
/* Select random square of the grid, to start with. */
x = 1 + Math.nextInt(lenx - 2);
y = 1 + Math.nextInt(leny - 2);
z = 1 + Math.nextInt(lenz - 2);
/* Mark this square as connected to the maze. */
maze[x][y][z] &= ~(QUEUED + IN_MAZE);
/* Remember the surrounding squares, as we will... */
for (d = 0; d < 6; ++d) {
if ((maze[x + dx[d]][y + dy[d]][z + dz[d]] & QUEUED) != 0) {
/* ...want to connect them to the maze. */
todo[todonum++] = [x + dx[d], y + dy[d], z + dz[d]];
maze[x + dx[d]][y + dy[d]][z + dz[d]] &= ~QUEUED;
}
}
/* We won't be finished until all is connected. */
while (todonum > 0) {
/* We select one of the squares next to the maze. */
n = Math.nextInt(todonum);
x = todo[n][0];
y = todo[n][1];
z = todo[n][2];
/* We will connect it, so remove it from the queue. */
todo[n] = todo[--todonum];
/* Select a random direction, which leads to the maze. */
do {
d = Math.nextInt(6);
}
while ((maze[x + dx[d]][y + dy[d]][z + dz[d]] & IN_MAZE) != 0);
/* Connect this square to the maze. */
maze[x][y][z] &= ~((1 << d) | IN_MAZE);
maze[x + dx[d]][y + dy[d]][z + dz[d]] &= ~(1 << (d ^ 1));
/* Remember the surrounding squares, which aren't... */
for (d = 0; d < 6; ++d) {
if ((maze[x + dx[d]][y + dy[d]][z + dz[d]] & QUEUED) != 0) {
/* ...connected to the maze, and aren't yet queued to be. */
todo[todonum++] = [x + dx[d], y + dy[d], z + dz[d]];
maze[x + dx[d]][y + dy[d]][z + dz[d]] &= ~QUEUED;
}
}
/* Repeat until finished. */
}
/* Add an entrance and exit. */
maze[1][1][1] &= ~WALL_ABOVE;
maze[lenx - 2][leny - 2][lenz - 2] &= ~WALL_BELOW;
}
/* Called to write the maze to an SVG file. */
this.printSVG = function () {
println("<svg lenx=\"" + (lenx * cell_width) + "\" leny=\"" + (leny * lenz * cell_width) + "\" version=\"1.1\" xmlns=\"http://www.w3.org/2000/svg\">\n"
+ " <g stroke=\"black\" stroke-lenx=\"1\" stroke-linecap=\"round\">\n" + this.drawMaze() + " </g>\n</svg>\n");
}
/* Main maze-drawing loop. */
this.drawMaze = function () {
var x, y, z;
var lenx = this.lenx;
var leny = this.leny;
var lenz = this.lenz;
var cell_width = this.cell_width
var outstring = ""
for (x = 1; x < lenx - 1; ++x) {
for (y = 1; y < leny - 1; ++y) {
for (z = 1; z < lenz - 1; ++z) {
var z_pos = z * leny * cell_width;
if ((this.maze[x][y][z] & WALL_ABOVE) != 0)
outstring += this.drawLine
(
x * cell_width,
y * cell_width + z_pos,
(x + 1) * cell_width,
y * cell_width + z_pos
);
if ((this.maze[x][y][z] & WALL_BELOW) != 0)
outstring += this.drawLine
(
x * cell_width,
(y + 1) * cell_width + z_pos,
(x + 1) * cell_width,
(y + 1) * cell_width + z_pos
);
if ((this.maze[x][y][z] & WALL_LEFT) != 0)
outstring += this.drawLine
(
x * cell_width,
y * cell_width + z_pos,
x * cell_width,
(y + 1) * cell_width + z_pos
);
if ((this.maze[x][y][z] & WALL_RIGHT) != 0)
outstring += this.drawLine
(
(x + 1) * cell_width,
y * cell_width + z_pos,
(x + 1) * cell_width,
(y + 1) * cell_width + z_pos
);
if ((this.maze[x][y][z] & WALL_FRONT) != 0)
outstring += this.drawLine
(
x * cell_width + cell_width/3,
(y + 1) * cell_width - cell_width/3 + z_pos,
(x + 1) * cell_width - cell_width/3,
y * cell_width + cell_width/3 + z_pos
);
if ((this.maze[x][y][z] & WALL_BACK) != 0)
outstring += this.drawLine
(
x * cell_width + cell_width/3,
y * cell_width + cell_width/3 + z_pos,
(x + 1) * cell_width - cell_width/3,
(y + 1) * cell_width - cell_width/3 + z_pos
);
}
}
}
return outstring
}
/* Draw a line, either in the SVG file or on the screen. */
this.drawLine = function (x1, y1, x2, y2) {
return " <line x1=\"" + x1 + "\" y1=\"" + y1 + "\" x2=\"" + x2 + "\" y2=\"" + y2 + "\" />\n";
}
}
/* Initialization method that will be called when the program is
* run from the command-line. Maze will be written as SVG file. */
function main(args) {
var m = new Maze();
m.createMaze();
m.printSVG();
}
/* execute the program */
main()
解决方案
使用位操作的最常见原因是因为它们快速并允许整数中的信息紧凑。
也就是说，这个脚本似乎在网格中的每个正方形上使用它们作为标志。
查看以下代码：
/* Define the bit masks */
var Constants =
{
WALL_ABOVE : 1,
WALL_BELOW : 2,
WALL_LEFT : 4,
WALL_RIGHT : 8,
QUEUED : 16,
IN_MAZE : 32
}
这些常数中的每一个都在整数中占据一点点。至 查看 如果设置了标志，则需要做的就是确定其位置是否设置为1（通常是通过该数字和比较为0）。至 放 一个标志，您只需设置该位值（通常是通过数字或数字来设置）。这就是位运算符所做的。
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