Shuffle an array as many as possible

Question

I have an array like this

[0,2,3]

The possible shuffling of this array are

[0,2,3], [2,3,0], [3,0,2], [3,2,0], [0,3,2],         


        

Answer 1

Try a recursive approach. Here's a hint: every permutation of [0,2,3] is either

• [0] plus a permutation of [2,3] or
• [2] plus a permutation of [0,3] or
• [3] plus a permutation of [0,2]

Answer 2

you don't need to recurse. The demo should make the pattern pretty clear: http://jsfiddle.net/BGYk4/

function shuffle(arr) {
        var output = [];
        var n = arr.length;
        var ways = [];
        for(var i = 0, j = 1; i < n; ways.push(j *= ++i));
        var totalWays = ways.pop();
        for(var i = 0; i < totalWays; i++) {
                var copy = arr.slice();
                output[i] = [];
                for(var k = ways.length - 1; k >= 0; k--) {
                        var c = Math.floor(i/ways[k]) % (k + 2);
                        output[i].push(copy.splice(c,1)[0]);
                }
                output[i].push(copy[0]);
        }
        return output;
}

this should output all possible "shuffles"

console.log(shuffle(['a', 'b', 'c', 'd', 'e']));