JS快排

var quicksort = function(arr){
    if(arr.length <= 1){
        return arr;
    }
    var pivotIndex = matn.floor(arr.length/2);
    var pivot = arr.splice(pivotIndex,1)[0];
    var left = [];
    var right = [];
    for (var i = 0; i < arr.length; i++){
        if(arr[i] < pivot){
            left.push(arr[i]);
        }else{
            right.push(arr[i]);
        }
    }
}

return quicksort(left).concat([pivot], quicksort(right));