If you have an NSMutableArray, how do you shuffle the elements randomly? (I have my own answer for this, which is posted below, but I'm new to Cocoa and I'm interested to know if there is a better way.) ...
I'm writing a number of articles meant to teach beginning programming concepts through the use of poker-related topics. Currently, I'm working on the subject of shuffling. As Jeff Atwood points out on CodingHorror.com, one simple shuffling method (iterating through an array and swapping each card with a random card elsewhere in the arra...
I am getting very frustrated because I cannot seem to figure out why Collections shuffling is not working properly. Lets say that I am trying to shuffle the 'randomizer' array. int[] randomizer = new int[] {200,300,212,111,6,2332}; Collections.shuffle(Arrays.asList(randomizer)); For some reason the elements stay sorted exa...
Hi, I am wondering if there is a "best" way to shuffle a list of elements that contains duplicates such that the case where array[i] == array[i+1] is avoided as much as possible. I am working on a weighted advertising display (I can adjust the number of displays per rotation for any given advertiser) and would like to avoid the same ad...
I need to randomly 'sort' a list of integers (0-1999) in the most efficient way possible. Any ideas? Currently, I am doing something like this: bool[] bIndexSet = new bool[iItemCount]; for (int iCurIndex = 0; iCurIndex < iItemCount; iCurIndex++) { int iSwapIndex = random.Next(iItemCount); if (!bIndexSet[iSwapIndex] && iSwapIn...
Is there any known algorithm that can generate a shuffled range [0..n) in linear time and constant space (when output produced iteratively), given an arbitrary seed value? Assume n may be large, e.g. in the many millions, so a requirement to potentially produce every possible permutation is not required, not least because it's infeasibl...
Hi, For a programming class I am creating a blackjack program for the first homework assignment. The professor has given us a sample Card class, which includes the method to add them to a deck. For her deck, she uses an ArrayList, which you can easily Knuth Shuffle with the Collections.shuffle() method. That method does not work for St...
While thinking about this question and conversing with the participants, the idea came up that shuffling a finite set of clearly biased random numbers makes them random because you don't know the order in which they were chosen. Is this true and if so can someone point to some resources? EDIT: I thnk I might have been a little uncle...
I read this post about card shuffling and in many shuffling and sorting algorithms you need to swap two items in a list or array. But what does a good and effecient Swap method look like? Lets say for a T[] and for a List<T>. How would you best implement a method that swaps two items in those two? Swap(ref cards[i], ref cards[n]); // ...
First of all, I do know about the Fisher-Yates shuffle. But lets say for arguments sake that I want to allow the user to pick a sort option from a Dropdown list. This list would include a "Random" option. Based on the result of their selection I just want to substitute in an IComparer instance for my sort. What would the IComparer lo...
I need to do an arbitrary reorder of a 7 bit value (Yes I know I should be using a table) and am wondering if there are any bit hacks to do this. Example: // <b0, b1, b2, b3, b4, b5, b6> -> <b3, b2, b4, b1, b5, b0, b6> // the naive way out = (0x020 & In) << 5 | (0x008 & In) << 2 | (0x040 & In) | (0x012 & In) >> 1 | ...
I need a function which returns an array in random order. I want to ensure that it is randomish but I have no idea how one would go about writing the tests to ensure that the array really is random. I can run the code a bunch of times and see if I have the same answer more than once. While collisions are unlikely for large arrays it i...
I've created a site for an artist friend of mine, and she wants the layout to stay the same, but she also wants new paintings she'd produced to be mixed into the current layout. So I have 12 thumbnails (thumb1 - thumb12) on the main gallery page and 18 images (img1 - img18) to place. The approach I thought of was to create an array of ...
it seems that this simple shuffle algorithm will produce biased results: # suppose $arr is filled with 1 to 52 for ($i < 0; $i < 52; $i++) { $j = rand(0, 51); # swap the items $tmp = $arr[j]; $arr[j] = $arr[i]; $arr[i] = $tmp; } you can try it... instead of using 52, use 3 (suppose only 3 cards are used), and run it 10,0...
How can I randomize the lines in a file using a standard tools on Redhat Linux? I don't have the "shuf" command, so I am looking for something like a perl or awk one liner that accomplishes the same task. ...
I was helping somebody out with his JavaScript code and my eyes were caught by a section that looked like that: function randOrd(){ return (Math.round(Math.random())-0.5); } coords.sort(randOrd); alert(coords); My first though was: hey, this can't possibly work! But then I did some experimenting and found that it indeed at least see...
I have a list of objects in python and I want to shuffle them. I thought I could use the random.shuffle method, but this seems to fail when the list is of objects. Is there a method for shuffling object or another way around this? import random class a: foo = "bar" a1 = a() a2 = a() b = [a1,a2] print random.shuffle(b) This will...
I am trying to write a code for a project that lists the contents of a deck of cards, asks how much times the person wants to shuffle the deck, and then shuffles them. It has to use a method to create two random integers using the System.Random class. These are my classes: Program.cs: using System; using System.Collections.Generic; u...
Hi, I would like to generate a random number less than 50, but once that number has been generated I would like it so that it cannot be generated again. Thanks for the help! ...
I have an array that I want to permutate randomly. In Java, there is a method Collections.shuffle() that can shuffle the elements of a List randomly. It can be used on an array too: String[] array = new String[]{"a", "b", "c"}; // Shuffle the array; works because the list returned by Arrays.asList() is backed by the array Collections.s...