chronological order number needs in index numbers to be changed as ndash

Hi all,

Here is the routine I use in IndexMatic 2 (script-in-progress). That's certainly equivalent to Bob's and/or Peter's approach, but why not sharing:

function makeSequences(/*Number[]*/numbers, /*String*/separator, /*String*/linker)
{
separator = separator || ", ";
linker = linker || "-";

if( numbers.length < 2 ) return numbers.join('');

var a = numbers.concat().sort(function(x,y){return x-y;}),
     sz = a.length-1, i = 0, i0 = 0, n = a[0], r = [];

var format = function()
     {
     r.push(a[i0] + ((i-i0)>1 ? linker+a[i-1] : ''));
     return i0=i;
     };

while( i<sz && ( n+1>=(n=a[++i]) || format()));
format();
return r.join(separator);
}


// Sample code:

var myTest1 = [ 1, 2, 4, 6, 9, 10, 11, 12, 13, 14, 15, 18, 19, 30 ];
alert( makeSequences(myTest1, ", ", "\u2013") );
// => 1–2, 4, 6, 9–15, 18–19, 30

var myTest2 = [ 5, 3, 4, 4, 6, 6, 9, 12, 1, 18, 21, 22, 22, 0, 8 ];
alert( makeSequences(myTest2, " | " ) );
// => 0-1 | 3-6 | 8-9 | 12 | 18 | 21-22

@+

Marc

Thanks for the fun morning algorithm exercise...

I think this will do it for you.

Regards

Bob

indexize = function( ar ) {
    var out = new Array();
    for ( var i = 0; i < ar.length; i++ ) {
        var a = i + 1;
        var current = ar[ i ];
        var concat = false;
        while ( parseInt( ar[ a++ ] )== ( current + 1 ) ) {
            current = ar[ a - 1 ];
            concat = true;
        }
        if ( concat ) {
            if ( parseInt( ar[ i ] ) + 1 == current ) {
                out.push( ar[ i ] );
                out.push( ar[ i + 1 ] );
            } else {
                out.push( ar[ i ] + "-" + current  );
            }
        } else {
            out.push( ar[ i ] );
        }
        i = a - 2;
    }
    return out;
}

var a = [ 1, 2, 4, 5, 7, 9, 11, 12, 15, 16, 17, 18, 19, 20, 22, 23, 25, 26, 27, 30, 31, 33, 34, 35, 36, 40, 41, 43,44,45,47,48,50 ];
$.writeln( "Input: " + a );
debugger;
$.writeln( "Output: " + indexize( a ) );