| JavaScript - Binary Sort for Strings | | Print | |
function sort( s )
{
if( s.length == 1 ) return;
else
{
var a = new Array( parseInt( s.length / 2 ) );
var b = new Array( s.length - a.length );
for( i = 0 ; i < a.length ; i++ ) a[i] = s[i];
for( i = 0 ; i < b.length ; i++ ) b[i] = s[i+a.length];
sort( a );
sort( b );
var ai = 0, bi = 0, i = 0;
while( ai < a.length || bi < b.length )
{
if( bi >= b.length ) s[i++] = a[ai++];
else if( ai >= a.length ) s[i++] = b[bi++];
else if( a[ai].compareTo( b[bi] ) <= 0 ) s[i++] = a[ai++];
else if( a[ai].compareTo( b[bi] ) > 0 ) s[i++] = b[bi++];
}
}
}
This is an extremely useful function, not only for sorting strings, but also for sorting the items in a list form element.
Following is an example of using this function with an array of strings:
<head>
<title>
JavaScript Professional Projects - Example Function
</title>
<script language="JavaScript">
<!--
var months = new Array( "January", "February", "March",
"April", "June", "July",
"August", "September", "October",
"November", "December" );
function display()
{
for( i = 0 ; i < this.length ; i++ )
{
document.write( this[i] + "<br>" );
}
}
Array.prototype.display = display;
function sort( s )
{
if( s.length == 1 ) return;
else
{
var a = new Array( parseInt( s.length / 2 ) );
var b = new Array( s.length - a.length );
for( i = 0 ; i < a.length ; i++ ) a[i] = s[i];
for( i = 0 ; i < b.length ; i++ ) b[i] = s[i+a.length];
sort( a ); sort( b );
var ai = 0, bi = 0, i = 0;
while( ai < a.length || bi < b.length )
{
if( bi >= b.length ) s[i++] = a[ai++];
else if( ai >= a.length ) s[i++] = b[bi++];
else if( a[ai].compareTo( b[bi] ) <= 0 ) s[i++] = a[ai++];
else if( a[ai].compareTo( b[bi] ) > 0 ) s[i++] = b[bi++];
}
}
}
function compareTo( s )
{
var len1 = this.length;
var len2 = s.length;
var n = ( len1 < len2 ? len1 : len2 );
for( i = 0 ; i < n ; i++ )
{
var a = this.charCodeAt( i );
var b = s.charCodeAt( i )
if( a != b )
{
return( a - b );
}
return( len1 - len2 ); }
String.prototype.compareTo = compareTo;
// -->
</script>
</head>
<body>
<table border=1 cellspacing="2" cellpadding="20">
<tr>
<td width=150><b>Unsorted</b></td>
<td width="150"><b>Sorted</b></td>
</tr>
<tr>
<td>
<script language="JavaScript">
<!--
months.display();
-->
</script>
</td>
<td>
<script language="JavaScript">
<!--
sort( months );
months.display();
-->
</script>
</td>
</tr>
</table>
</body>
</html>
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