Forum Moderators: open
<html>
<head>
<title>ROTATING AN ARRAY</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script type="text/javascript">
function loadit(){
var x="";
var y="";
var outputthis="";
var exampleArrayNumber="";
var exampleArray =[['<B>TL</B>','TR'],['BL','BR']];outputthis +="<p>The Array TL TR BL BR</p>";
for (x=0;x<2;x++) {
for (y=0;y<2;y++) {
exampleArrayNumber = exampleArray[x][y];
outputthis +=exampleArrayNumber;
}
outputthis +="<br>";
}
outputthis +="<p>Rotated 90 degrees</p>";
for (y=0;y<2;y++) {
for (x=1;x>-1;x--) {
exampleArrayNumber = exampleArray[x][y]
outputthis +=exampleArrayNumber;
}
outputthis +="<br>";
}
outputthis +="<p>Rotated 180 degrees</p>";
for (x=1;x>-1;x--) {
for (y=1;y>-1;y--) {
exampleArrayNumber = exampleArray[x][y]
outputthis +=exampleArrayNumber;
}
outputthis +="<br>";
}
outputthis +="<p>Rotated 370 degrees</p>";
for (x=1;x>-1;x--) {
for (y=0;y<2;y++) {
exampleArrayNumber = exampleArray[y][x]
outputthis +=exampleArrayNumber;
}
outputthis +="<br>";
}
document.write(outputthis);
}
</script>
</head>
<body>
<script language="JavaScript" type="text/JavaScript">
loadit()
</script>
</body>
</html>
function loadit()
{
var sq =[['<B>TL</B>','TR'],['BL','BR']];
sq.rotate = rotateSquare;
sq.toString = squareToString;
var br = "<br>";
var output =
"<h4>The Array: [['<B>TL</B>','TR'],['BL','BR']]</h4>"
+sq;
for(var k=1;k<4;k++)
output+= "<p>Rotated "+(k*90)+" degrees</p>"
+ sq.rotate(1);
document.write(output);}
function rotateSquare(n)
{
n=(4+~~n%4)%4;
while(n--){
this[1].push( this[0].pop() );
this[0].unshift( this[1].shift() );
}
return this;
}function squareToString()
{
return this.join("<br>").replace(/,/g,"");
}
rotateSquare:
Argument n: number of 90 deg rotations.
Truncates non-integer values of n (using ~~n):
2.3, 2.78 become 2
-2.3, -2.78 become -2
Accepts negative n (although not demo'd here)
This is done the lazy way, using "clock arithmetic". The modulus operator, %, in Javascript (and some other languages) is inconvenient for this task, so the expression: n=(4+n%4)%4 ensures that eg -3 becomes 1.
squareToString:
When an object is used in alert or document.write etc, its toString method is called. We override this for the outer array with a custom method that produces the HTML.
It assumes, for convenience, that the actual elements do not contain any commas.
----------------------------------------------------------
It might be better to create a Square data type do all this.
The "square" methods could be inherited rather than directly attached.
Another question. If I take the while loop out of the function rotateSquare the script still returns the same values.
function rotateSquare(n)
{
// n=(4+~~n%4)%4;
// while(n--){
this[1].push( this[0].pop() );
this[0].unshift( this[1].shift() );
//}
return this;
}
Whats the point of
n=(4+~~n%4)%4;
for(var k=1;k<8;k++)
And!
if the array was
var sq =[[4,8,5,5,5,5,5,3,5],
[5,5,5,5,5,7,5,5,8],
[5,5,5,5,5,5,5,5,5],
[5,6,3,5,2,5,5,5,5],
[5,9,5,1,5,3,5,6,5],
[5,5,5,5,7,5,1,4,5],
[5,5,8,5,5,5,5,5,5],
[2,5,5,6,4,5,5,5,5],
[5,1,5,5,5,5,5,5,7]];
then .. lol .. sorry tried to make the original question as basic as possible. The above is what im tring to rotate.
I shall thank you scurry off and try and re-invent the wheel. Thanks.
If I take the while loop out of the function rotateSquare the script still returns the same values
Since we are only asking for one 90 degree rotation each time, the function's full abilities aren't actually used. If we did, say: rotateSquare(3) then it would make a difference if the loop were removed.
Whats the point of n=(4+~~n%4)%4
Perhaps it would be easier written as:
if(n > 0)
n = Math.floor(n) % 4;
else if(n < 0)
n = (Math.ceil(n)%4) + 4;
1) Only use integer part of n
2) Restrict n to the range [0-3]
This is because eg:
- 5 90 deg rotations is the same as 1,
- 1 90 deg anti-clockwise rotation is the same as 3 clockwise.
And!
if the array was
Ah.. Now that will require something different.
I take it that "rotation" in this case is a physical one. The sort that would turn a 3 by 2 matrix into a 2 by 3 after a 90 degree rotation
I take it that "rotation" in this case is a physical one. The sort that would turn a 3 by 2 matrix into a 2 by 3 after a 90 degree rotation
Thanks.
var arr =
[
["A","B","C","D"],
["D","E","F","G"],
["H","I","J","K"]
];arr.toString = array2ToString;
array2Rotate(arr,1);
alert(arr);/* change "\n" to "<br>" */
function array2ToString()
{
return this.join("\n").replace(/,/g,"");
}function array2Rotate(A,n){
var nRows,nCols;
var rotate = {
1 : function(){
for(var k=0;k<nCols;k++)
A.push(columnReversed(k));
A.splice(0,nRows)
},2: function(){
A.reverse();
for(var k=0;k<nRows;k++)
A[k].reverse();
},3: function(){ this[1](); this[2](); }
}function columnReversed(x){
var col = [], k=nRows;
while(k) col.push(A[--k][x]);
return col;
}
/* start */
n = (4+~~n%4)%4;
nCols = A[0].length;
nRows = A.length;if(n) rotate[n]();
return A;
}
Just noticed
the cat sat on the
the mat in the array!
:)
