Geek asks and answers

Javascript: sort an array by input number. Must appear randomly sorted

I have a javascript array that I would like to sort according to the specified number or string. I would like the array to look randomly sorted, but the array will always sort the same if the input was “6543”, for example.

+3
source share
3 answers

Javascript itself does not offer this functionality - its RNG cannot be sown. There are still different approaches that can be taken. Here is one. The seed must be more than one (or the same array will be returned), and must be larger than the size of the array for sufficient "randomness".

Array.prototype.deterministicShuffle=function(seed){
    // A little error handling, whynot!
    if(!seed)
        throw new Error("deterministicShuffle: seed not given, or 0");

    var temp,j;

    for(var i=0; i<this.length; i++){
        // Select a "random" position.
        j = (seed % (i+1) + i) % this.length;

        // Swap the current element with the "random" one.
        temp=this[i];
        this[i]=this[j];
        this[j]=temp;

    }

    return this;
}

// Try it out, Aaron!    
alert([0,1,2,3,4,5,6,7,8,9].deterministicShuffle(6543));
alert([0,1,2,3,4,5,6,7,8,9].deterministicShuffle(6544));
alert([0,1,2,3,4,5,6,7,8,9].deterministicShuffle(6545));
+3
source

Use the shuffle function and replace it Math.random()with a random number generator where you can set your own seed . Then set the seed to your entry number.

+2
source

, , .

As Alex suggested, the site he provided has a good shuffle feature. I combined this with another function to get the ascii value of the seed.

You should strongly consider changing my example to a hash input. Otherwise there will be many collisions.

Here is the code:

<script>

    // http://sharkysoft.com/tutorials/jsa/content/018.html
    function ascii_value (c)
    {
        // restrict input to a single character
        c = c . charAt (0);

        // loop through all possible ASCII values
        var i;
        for (i = 0; i < 256; ++ i)
        {
            // convert i into a 2-digit hex string
            var h = i . toString (16);
            if (h . length == 1)
                h = "0" + h;

            // insert a % character into the string
            h = "%" + h;

            // determine the character represented by the escape code
            h = unescape (h);

            // if the characters match, we've found the ASCII value
            if (h == c)
                break;
        }
        return i;
    }

    // http://snippets.dzone.com/posts/show/849
    shuffle = function(o,seed){ //v1.0

        for(var j, x, i = o.length; i; j = parseInt(seed / (o.length * 255) * i), x = o[--i], o[i] = o[j], o[j] = x);
        return o;
    };


    function seedSort (string){
        var charList = string.split('');
        var seedValue = 0;
        for(var i in charList){

            seedValue += ascii_value(charList[i]);

        }
        return seedValue;
    }

    document.write(shuffle([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],seedSort("bob")));
    document.write("<br>");
    document.write(shuffle([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],seedSort("steve")));
    document.write("<br>");
    document.write(shuffle([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],seedSort("david house")));
    document.write("<br>");
    document.write(shuffle([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],seedSort("acorn22")));


</script>

This will create

8,2,3,4,5,6,7,0,9,1
4,9,3,0,5,6,7,8,1,2
8,0,6,1,5,2,7,3,9,4
4,8,3,0,5,6,7,1,9,2

... which seem random. I would suggest big seeds.

0
source

More articles:


All Articles