I am creating a mathematic app for iOS that contain simple tasks for children.
My objective is: compare an user answer with a defined answer in the particular task.
For example: users have to answer on questions e.g. 10 + 6 = 16, 20 - 2 = 18 etc...
But also I have task that users must solve in few steps.
For example: Ben went 5 miles. In the next day he went 10 miles. To get home, he needs to walk 20 miles. Question is - how many miles does he needs to walk to get home?
So the solution is next:
5 + 10 = 15
20 - 15 = 5
Answer: 5 miles
Well, I have created all my tasks in the JSON format and now I can compare user answer and right answer based on the string. But now I have a little bit problem. For example if I compare full string thats means I don't allow users move components. For example user can create next solution:
10 + 5 = 15 but also he can create another variant 5 + 10 = 15.
20 - 15 = 5
So, there are no problems if I will keep all anwers, because I will analyze all strings and it will be perfect. But I think this is bad solution to keep all answers in JSON (I mean all variant answers)
But, maybe it is only one solution. What do you think?
Ok so you don't want to transfer too much Data via JSON format. I would suggest using brackets to ensure order of operations. Evaluate the answer to make sure it is the correct one. On the server, you could run a script that cuts the numbers out and put them into an array list of some sorts. Then check if all the numbers in the correct answer are in the numbers in the user submitted string. If you are only doing addition, then your fine but if you introduce new operations like division or modulo, you need to use brackets are evaluate each operation by expanding brackets. For example, you would have an answer like 10+(9+2). Evaluate 9+2 first and ensure that all the operations that are happening in the brackets are correct and then evaluate the answer in that set of brackets with the operations on the outside. Don't do too many computations on the phone though.
Good luck.
If we just have math problems it may be possible to verify answers on the fly.
Double check that the user input matches the correct answer using javascript
You can use eval() to do this
Related
I don't think this matches any existing question but it seems kind of fundamental.
I have a variable full of ranks. Think of it like people who ran a marathon and their places. But there are lots of draws so there might be 5 firsts and 4 seconds and 9 thirds and so on.
Each case has a variable with their place except the people who finished third are not actually third. They are joint 10th from the above figures. The people who finished second are joint 6th.
How do I create a new variable with the marathon runners actual places in the race?
If I understand right, you want the Nth place to reflect the number of actual people above in the list?
Here is a way to do that:
sort cases by OrigPlace.
compute MyPlace=OrigPlace.
if $casenum>1 and OrigPlace<>lag(OrigPlace) MyPlace=$casenum.
if $casenum>1 and OrigPlace=lag(OrigPlace) MyPlace=lag(MyPlace).
exe.
Well one line is not enough to capture that question so ill explain it here.
Earlier today i was in a zoom meet where there are 12 members and we were split into different breakout rooms. After 30 mins we were shuffled and the host made sure to use a different combinations such that no two people who were in the same breakout room was in the same breakout room now. The host atleast tried to minimize the repetitions.
So my question is how many such combinations can we make on a group such that no two people who were in a meeting earlier repeat themselves.
If you could tell me in a algorithmic way, i will understand it.
Edit:
Let me further explain my problem with a use case:
Suppose there are 12 people in a zoom meet who are to be divided up into breakout rooms. Let me form 4 breakout rooms with 3 in each group.
so let the combination be [1,2,3][4,5,6][7,8,9][10,11,12].
the first iteration could have been anything really.
now the problem starts.
for the next combination i have to make sure that the breakout rooms cannot have the same people forming it.
so keeping this in mind i'll form the group as: [1,5,7][4,8,12][2,6,11][3,9,10].
wow. did you just see that? i had to make sure that no two people who were in a group earlier, are present in a single group presently. So my question is how do i write an algorithm for this problem.
math related questions fit better in https://math.stackexchange.com/
to your question:
i assume breakout rooms mean pears of 2?
-> everyone can match with 11 others - so basically 11 rounds?
There are no conflicts necessarily that reduce the rounds, if you organized matches from the start on.
Edit:
If you instead looked for the commonly school question:
Suppose there is a group of 12 people. In how many different ways can the 12 people be split into six pairs?
Then there are same matches allowed as long as one pair changes and the result would be
12!/(2^6 x 6!)
see: here
Edit after Clarification:
Well I only know Primary math and would still recommend https://math.stackexchange.com/ : )
My unqualified guess would be you have your total Permutations of 12! / (12-3)! Which are only
12! /(3! *(12-3)!) Combinations and then reduce it by all non-valid Combinations?
( 12! / (3! *(12-3)!) ) / 4 = 55?
Or 12! / (4! *(12-3)!) = 55?
If you need this for some kind of school, I recommend learning basics first. The solution will not help you in your class!
https://www.calculator.net/permutation-and-combination-calculator.html?cnv=12&crv=3&x=76&y=12
https://math.stackexchange.com/questions/35684/combination-of-splitting-elements-into-pairs
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Youtube provides two sorting options: Newest first and Top comments. The "Newest first" is pretty simple that we just sort the comments by their post date. But the "Top comments" seems to be a lot more complex than just sorting by "thumb up"s.
After a short research, I found out that the order of comments depends on those things:
Number of "thumb up"s and "thumb down"s
Post date
Number of replies to that comment
But I don't know how Youtube uses this information to decide the order, like what information is more important and what is less important.
Is there any article about this topic that I could refer to?
Thanks!
I have the answer to your question.
After searching the internet for the answer to this, I never found precisely what I was looking for. So, my colleagues and I decided to experiment using the system with the Youtube comments.
First of all, we sorted what we believed to be popular videos into one section, average videos into another, and less popular into the last. There were 200 videos in each section, and after days of examining we started to notice a pattern. We found that you were right about the three things required, but we also dove a little deeper and found an additional variable.
The Youtube comment system depends on four things:
1) Time it was posted,
2) Like/dislike ratio of a comment,
3) Number of replies,
4) And, believe it or not, WHO posted it.
The average like/dislike ratio of every public comment you've ever posted builds into it, as (what we predicted) they believe that those with low like/dislike ratios would post comments that many people do not like or simply disagree with.
There is an algorithm to it, and it is quite simpler than you might think. Basically there are these things that we called "module points," and you get a certain one based on these four factors. First, here's the things you need to know about module point conversion with TWO of the factors:
For the like/dislike ratio on the comment, multiply that number by ten.
For the amount of replies (NOT from the original poster) that the comment has, there are two module points.
These are the two basic factors that tell the amount of module points the comment has.
For example, if a comment had 27 likes and 8 dislikes, then the ratio would be 3.375. Multiplying by 10, you would then have 33.75 module points. Using the next factor, amount of replies, let's say this comment has 4 direct replies to it. Multiplying 2 by 4, we get 8. This is the part where you add 8 onto the accumulative module points, giving you a total of 41.75 module points.
But we're not done here; this is where it gets tricky.
Using the average like/dislike ratio of a person's total comments that they've ever posted publicly, we found that the formula added onto the accumulative module points is this:
C = MP(R/3) + (MP/10)
where C = Comment Position Variable; MP = Module Points; R = Person's total like/dislike ratio
Trust me, we spend DAYS just on this part, which was probably the most frustrating. Even though the 3 and the 10 within this equation seem random and unnecessary, so far all of the comments we tested this equation on passed the test, but did not pass the test when those two variables were removed. After this equation is done, it gives you a number that we named to be the Position Variable.
However, we are not even done yet, we still haven't talked about time.
I was actually quite surprised that this part didn't take as long as I expected, but it sure was a pain doing this equation every single time for every comment we tested. At first, when testing it, we figured that the time was just there to break the barrier if 2 comments had equal Position Variables.
In fact, I almost called it a wrap on the experiment when this happened, but upon further inspection, we found out there was more to do. We found that some of the comments outranked each other that had the same Position Variable, but the timing seemed to be random! After a few days of inspection, here is where the final result comes in:
There is yet ANOTHER equation that we must find before applying the 4th variable. Using another separate equation, here's what our algebraic deductions came down to:
X = 1/3(S/10 + A) x [absolute value of](A - 3S)
where X = Timing Variable; S = How long ago the video was posted in minutes; A = How long ago the comment was posted in minutes
I wish I was making this up, but unfortunately this is how complicated the system is. There are mathematical reasons behind the other variables, but they are far too complex to explain, it will probably take up atleast three paragraphs worth of explaining. We tested this equation on more than 150 comments, all of them checked out to be true.
Once you find X, which is what we called the Timing Variable, all you have to do from here is apply it to this equation:
N = X(C/4 + 1)
where X = Timing Variable; C = Positioning Variable
N is the answer to all your problems.
This is the final equation, the final answer. The simple conclusion: the higher N, the higher up the comment is.
Note: Special thanks to my colleagues: David Mattison, Josh Williams, Diego Mendieta, Steven Orsette, and Kyle Shropshire. I could have never found out this without them and the work they put into this.
I saw a question here recently and bookmark it for further thought. This is the question. What I can't determine myself is if this question is really interesting or nothing special?
Why this is, its because it looked to me that it had a real simple answer sort by lowest distance*time product, or am I missing something obvious?
I can explain the reason why it looked simple to me:
Distance is always somewhat constant no matter when or where the query is ran, meaning that if: My home is at point A and there is a post at point B and another post at point C, no matter when I ran the query I will always get the constant values say 5km & 7km.
The time offset since the post looks like it's also somewhat constant in a sense that it grows equally for all posts. Meaning that if post B is from 2004 and post C is from 2009, now they will be 7 years and 2 years ago respectively. So next year it will be 8 and 3 years ago and so on.
Adding a weight value(s) to 'tweak' the distance & time is not any helpful (not needed) since (taking the values from the two post above) 5*7*alpha will always be more then 2*7*aplha hence no matter when we ran the query post C (2*7*aplha) will always be the 'closest most recent'
Also adding a weight constant to 'tweak' the results seems like it's no longer going to product the most closest and recent but will favor either or in which case I may as well sort by most recent and then by most closest or vise versa. But this is no longer the closest more recent but either the closest then more recent or more recent then closest so both those questions are trivial I believe. So this is why I think tweaking is not a good idea no matter what units are chosen to represent the time offset and distance.
Addition doesn't work as well as multiplication I think but distance*time seems to be sufficient to always get the correct result.
So this is what I was thinking but then I thought, no that can't be that simple. So what am I missing here?
The best way to determine the desired sorting expression would be to let some human beings sort some items manually and deduce the expressions from their answers. It may well be that different persons would give different answers, so that one single expression can't accommodate everyone.
There are other useful polynomial expressions such as t*d + A*t + B*d, where t and d are time and distance. Maybe more precise results can be achieved if we introduce one more polynomial degree, so that expression becomes t*d + A*t*t + B*d*d + C*t + D*d. Only from answers of real humans can you devise this formula.
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I am a beginner IT student and doing a project for my programming logic and design class. I need to create a psuedocode for a dice game that allows you 2 rolls with 5 dice. On the first roll you get to pick 1 die to keep. The computer then rolls the other 4 dice and calculates you're score based on what you rolled. There are 3 rolls per game and the total score is displayed. Rolling nothing takes points away. The scoring is: 2 of a kind=50 points, 3 of a kind=75 points, 4 of a kind=100 points and nothing subtracts 50 points.
The whole problem I have is I dont even know where to start. I think I need this to repeat 3 times, but what variables do set? Please someone help me, I cant really ask my instructor because he is outside smoking the whole class and everything I have learned about this class mostly came from the internet and reading the book. I dont want to fail this class...someone please help me through this???
First of all don't panic. What you are about to do is break the task down into small steps.
Pseudo-code is not really code - you can't use it directly as a language, but instead it is just plain english to describe what it is you are doing and the flow of events.
So what are the initial steps to get you started?
Ask yourself what are the facts, what do you know exist in advance. These are the "declarations" that you make.
You have five dice. Each is a seperate object so each gets it's own variable declaration
dice_1
dice_2
dice_3
dice_4
dice_5
Next decide if each die has an initial value
dice_1 initial value = 0
etc...
Next you know that you have to throw the dice a number of times. Throwing is a variable with an initial value
turns initial value = 2
turns_counter initial value = 2
You should be getting the idea now. Are there other things you should declare in advance? I think so!
Next you have to decide what it is you are doing step by step. Is it just a sequence of events or is it repeating? If it's repeating how do you get it to stop?
While turns_counter is less than 2
Repeat the following:
turns_counter = turns_counter + 1
if turns_counter = 2
Throw. Collect_result. Sum_result.
else
Throw. Collect_result. Sum_result. Remove_a_dice.
endif.
perhaps you have to tell the reusable code which objects they are going to be working with? These are parameters that you pass to the reusable code Throw(dice_1) perhaps also you need to update some variables that you created? do it in the reusable code with or without passing them as parameters.
This is by no means complete or perfect, but you should get the idea about what's going on and how to break it down. It could take quite a while to do.
Most languages provide a pseudo-random number generator function that returns a random number within a certain range. I would start by figuring out which language you'll use and which function it provides.
Once you have that, you will need to call it for each roll of each dice. If you are rolling 5 dice, you would call it 5 times. And you would call it 5 more times for a second roll.
That's a start anyway.
You have already almost answered the question by simply writing it down here. There is no strict definition of what pseudocode is. Why don't you start by re-writing what you've described here as a sequence of steps. Then, for each step simply refine that step further until you think you've made it as fine-grain as you like.
You could start with something like this:
Roll 5 dice.
Pick 1 die to keep.
Rolls the other 4 dice
Calculate the score.
// etc...
Quite weird to think that it's easier to ask SO than your instructor! :)
The easiest way to get started on this is to not rigorously bind yourself to the constraint of a specific language, or even to pseudocode. Simply, in natural English, write out how you would do this. Imagine that YOU are the computer, and somebody wants to play the game with you. Just imagine, in very specific detail, what you would do at each potential step, i.e.
Give the user 5 dice
Ask the user to roll them
From that roll, allow the user to pick one die to keep
...etc. Once you have done this, and you are sure it is correct, start transforming it into pseudo code by thinking about what a computer would need to do to solve this problem. For instance, you'll need a variable keeping track of how many points the user as, as well as how many total rolls have occurred. If you were very specific in your English description of the problem, this should mean you basically only need to plug pseudo code into a few sentences you already have - in other words, you're just substituting one type of pseudo code for another.
I'd like to help, but straight-up providing the pseudo code wouldn't be very helpful to you. One of the hardest steps in beginning programming is learning to break a problem down into its constituent elements. That type of granular thinking is unintuitive at first, but gets easier the more time you spend on it.
Well, pseudo-code, in my experience, is best drawn up when you pretend you're writing up the work for someone else to do:
THINGS WE NEED
Dice
Players
Score
THINGS WE TRACK
Dice rolls
Player score
THINGS WE KNOW
(These are also called constants)
Nothing (-50)
2 of a kind (+50)
3 of a kind (+75)
4 of a kind (+100)
All of these are vital tools to getting started. And...well, asking questions on stackoverflow.
Next, define your "actions" (things we do), which utilizes the above known things that we will need.
I would start the same place I always do: creating our things.
def player():
"""Create a new player"""
def dice():
"""Creates 4 new, 6 sided dice"""
def welcome():
"""Welcome player by name, give option to quit"""
def game():
"""Initialize number of turns (start at 0)"""
def humanturn():
"""Roll dice, display, ask which one they'll keep"""
def compturn():
"""Roll four dice"""
def check():
"""Check for any matches in the dice"""
def score():
"""Tally up the score for any matches"""
def endturn():
"""Update turn(s), update total score"""
def gameover():
"""Display name, total score, ask for retry"""
def quit():
"""Quit the game"""
Those are your components, all fleshed out in a very procedural manner. There are many other ways to do this that are much better, but for now you're just writing the skeleton of an idea. You may be tempted to combine many of these methods together when you're ready to start coding, but it's a good idea to separate everything until you're confident you won't get lost chasing down a bug.
Good luck!