----------------------------------- skootles Sun Oct 02, 2005 12:48 pm Randint from a set of numbers? ----------------------------------- Wow... it's been a long time since I've been here :P But anyways, to the problem: I want my program to choose a random number from a list of numbers. Right now, I just want the list to be from 1-8, so the list (obviously) would be: 1,2,3,4,5,6,7,8. Now, I could just do this: randint (variable,1,8) But, I want it so that it only picks each number once. So, I was wondering if there was a way, for example, when the program selects... let's say... 5, it would then drop 5 from the list of numbers to choose from. Thus, the list would now be: 1,2,3,4,6,7,8 If that wasn't specific enough, I'll try to go into further detail. ----------------------------------- beard0 Sun Oct 02, 2005 1:07 pm ----------------------------------- Try putting your list of numbers in a flexible array (if you don't know what they are, the Turing help file is a good reference). Select a random number between lower(arrayName) and upper(arrayName), use that as your index. Then shuffle values down through your array, to replace the element you just "used", and remove the last element of your array - it is now ready for another selction. ----------------------------------- skootles Sun Oct 02, 2005 1:14 pm ----------------------------------- Arrays... I'm just starting to use those with turing. I've used them in VB, but only lightly. Anyways, thanks, I'll look up flexible arrays. :wink: ----------------------------------- [Gandalf] Sun Oct 02, 2005 2:05 pm ----------------------------------- Yep, I would do it like beard0 said. For any kind of 'list' you will for sure need to know arrays. ----------------------------------- Cervantes Sun Oct 02, 2005 6:46 pm ----------------------------------- "]Yep, I would do it like beard0 said. For any kind of 'list' you will for sure need to know arrays. What about [url=http://www.compsci.ca/v2/viewtopic.php?t=9284]Linked Lists? :) ----------------------------------- beard0 Sun Oct 02, 2005 7:01 pm ----------------------------------- Probably a better idea from a programming point of view, but the array solution is probably an easier one to use. For someone just starting to use arrays, pointers may be a little too complex. ----------------------------------- [Gandalf] Sun Oct 02, 2005 7:10 pm ----------------------------------- "]Yep, I would do it like beard0 said. For any kind of 'list' you will for sure need to know arrays. What about Would you be doing that without array knowledge? ----------------------------------- Cervantes Sun Oct 02, 2005 7:11 pm ----------------------------------- Ah, yes. I meant that solely as a comment to Gandalf. In fact, I was pondering whether to add a comment such as, "warning to skootles: clicking link may cause brain to explode". ----------------------------------- TokenHerbz Sun Oct 02, 2005 9:08 pm ----------------------------------- Array's are fairly simple, though the 2D arrays (which you dont need to know right now, but soon) can be a little more complicated... Anyways, i wrote the code you strived for, so if your really stuck, just post here, and ill show you the code, and explain to you how it works... But you must give it a good shot, its the only way to learn :) Good luck.! ----------------------------------- Tony Mon Oct 03, 2005 8:27 am ----------------------------------- Anyways, i wrote the code you strived for is it anything like [url=http://www.compsci.ca/v2/viewtopic.php?t=2184]this? :think: ----------------------------------- TokenHerbz Mon Oct 03, 2005 1:23 pm ----------------------------------- No :(... im not so good at making efficiant code... this was mine... var maxnum: int := 10 %%Enter here your max number var number: int %%This here is your number var used: array 1 .. maxnum of boolean %%this will tell you if the numbers used or not for i : 1 .. maxnum %%use a for statment to declare the array variable's used(i) := false %%sets all the numbers NOT declared end for loop %%to keep the program going for i: 1 .. maxnum %%use this for cause it holds the variables need'd (booleans) randint(number,1,maxnum) %%randomizes your number if number = i then %% if the random number = the one in the for if used(i) = false then %%checks to see if the numbers been used put number %%puts the number used(i) := true %%now marks the number as been used end if end if end for end loop Mine might not be as efficiant, but it works, i have problems making efficiant code, and i think thats my weak point... I must learn, or think more about how i can accomplish this... Nice code though Tony. ----------------------------------- codemage Mon Oct 03, 2005 1:50 pm ----------------------------------- This would be a slighly savvier method of implementing the main area of code, if you were to only use arrays. (The for & loop are switched, and there are a few other efficiency tweaks). You essentially have parallel arrays here; one of them is a virtual array existing between 1 and maxnum. Using arrays for this sort of code is very efficient with a small, consecutive array size. With really big nubmers, unsorted data types aren't so clean. for i : 1 .. maxnum loop number := Rand.Int (1, maxnum) if used (number) = false then put number used (number) := true end if end loop end for ----------------------------------- beard0 Mon Oct 03, 2005 2:49 pm ----------------------------------- This would be a slighly savvier method of implementing the main area of code, if you were to only use arrays. Oh? Tony's is much better, as your method creates a random amount of wait time, incresing in expected duration each time through. It is actually quite inneficient. ----------------------------------- Tony Mon Oct 03, 2005 3:35 pm ----------------------------------- codemage - the unsorted list of unique number is what we're after. in your code forloop is not needed as the inside loop never exits :lol: beard0 points out the core difference in approaches. The idea is that when randomly picking a number you have a deminishing chance of getting a number that wasn't used yet. Example -- scramble 100 numbers in random order. randomly picking 1st unsorted number - 100% randomly picking 50th unsorted number - 50% randomly picking 100th unsorted number - 1% on average you make edit: 5 tries per number to be sorted (though you don't really notice that until you get into the last few numbers) ----------------------------------- beard0 Mon Oct 03, 2005 7:23 pm ----------------------------------- on average you make two tries per number to be sorted. I get an average of 5.187378 tries per number to be sorted. :D var x : real := 0 for i : 1 .. 100 x += 100 / i end for put x/100 ----------------------------------- md Mon Oct 03, 2005 9:09 pm ----------------------------------- Since I'm too lazy to read all those people's posts; and since I might have a better solution anyways... Why not just create an array (seem's you can't live without them), fill it with your data set (numbers), shuffle it (key), and then just step through the array. Since I'm not much of a turing expert (ie. not at all) I'll write it in psudo-pascal which is a fairly simple language to grasp. const UPPER_BOUND = 8; (* or whatever number you want *) var data:array ----------------------------------- beard0 Mon Oct 03, 2005 10:37 pm ----------------------------------- Since I'm too lazy to read all those people's posts; and since I might have a better solution anyways... You'd have done well to read them. This isn't what was wanted (unless, as is possible, I'm misunderstanding the pascal). It seems to me that your solution allows repeat output of the same number from the set: This is undesirable. Check out Tony's solution, as it seems to me by far the best. ----------------------------------- skootles Tue Oct 04, 2005 12:09 am ----------------------------------- Well, I didnt read most of the posts after Tony's (Didn't understand them much :P), but here's basically what I wanted (modified version of Tony's code): var size:int :=7 % Changed based on the letters in the word var randN:int var numbers:array 1..size of int var word : string := "cookies" % Will be changed later for i:1..size numbers(i):=i end for for decreasing i:size ..1 randN := Rand.Int(1,i) put word(numbers(randN)) numbers(randN):=numbers(i) end for Thanks for all the help :wink: ----------------------------------- TokenHerbz Tue Oct 04, 2005 1:29 am ----------------------------------- scootles, dont use the code if you dont understand it... I want you to try it on your own now, and see if you can get it to work. ----------------------------------- codemage Tue Oct 04, 2005 8:14 am ----------------------------------- I missed Tony's complete solution. I'm aware of the inefficiency of the code I posted (see post). Like I explained, if the array was much larger, there'd be all sorts of wasted cycles. The snippet I posted was a re-write of the code done by tokenherbz - and wasn't meant to be a "best" solution. ----------------------------------- Tony Tue Oct 04, 2005 8:14 am ----------------------------------- I get an average of 5.187378 tries per number to be sorted. You're right. Here's another fun program const limit : int := 100 for try : 1 .. 10 var c : int := 0 for i : 1 .. limit loop c += 1 exit when Rand.Int (1, limit) >= i end loop end for put "run #", try, ": ", c / limit, " tries per number" end for ----------------------------------- skootles Tue Oct 04, 2005 10:38 am ----------------------------------- scootles, dont use the code if you dont understand it... I want you to try it on your own now, and see if you can get it to work. I understand the code I'm using (see above), so I think I'm good for now. ----------------------------------- TokenHerbz Tue Oct 04, 2005 10:34 pm ----------------------------------- Tony i ran your "fun" program and here where my resaults. run #1: 4.53 tries per number run #2: 8.15 tries per number run #3: 4.56 tries per number run #4: 4.46 tries per number run #5: 5.45 tries per number run #6: 5.79 tries per number run #7: 4.74 tries per number run #8: 5.35 tries per number run #9: 4.36 tries per number run #10: 4.25 tries per number What does this mean? i dont get what the test does? I ran it over and over and... Lowest number reached: 3.31 Highest number reached: 9.43 ----------------------------------- beard0 Tue Oct 04, 2005 10:42 pm ----------------------------------- Tony i ran your "fun" program and here where my resaults. .... What does this mean? i dont get what the test does? I ran it over and over and... Lowest number reached: 3.31 Highest number reached: 9.43 It is a simulation of the bad method used above, with uncertain execution time. The program that I wrote in the post that Tony refers to computes the expected average number of guesses per number in each trial (for 100 numbers), using mathematical probabilities. Tony's actually runs 10 trials, to see the avergae number of guesses per number performed. As Tony's program is run over and over again, the average should tend towards my computed value. ----------------------------------- Tony Wed Oct 05, 2005 7:30 am ----------------------------------- Highest number reached: 9.43 This means that during such an odd run, your program had to pick a random number 943 times before finding enough to order 100 items.