Puzzles & Programming Problems (Think Like a Programmer) 

Inspired by the talk in this comment section of this video, I've created a new video about performance and efficiency. I discuss what the terms mean, why we should care about this, and why we sometimes shouldn't. Check it out here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Xs-lY15vEec.html

This comment section reminds me of something a senior programmer once told me. He said that there is a world of difference between the attitude of an inexperienced vs experienced programmers(with mid-level being the worst). Senior developers are much more nurturing and understanding while inexperienced developers have a tendency to berate others for mistakes/shortcomings/lack of knowledge. Most here didn't understand the point of the first problem and the lesson he was trying to convey. People just wanted to make themselves look smart while in reality looking very cringey.

One thing that's helped me a lot is whenever you see a 'for' loop or need one, instantly fill it in, in your mind, with 'for each'.

I have been programming for 35 years. It is always good to go back to basics and review logic. It is like excercising your brain. Especially when you are learning a new language. Good video series

I have 8 years of programming experience, but this is a great video. I actually benefited from this.

my first course in my computer science education was just on how to think like this our professor was a master problem solver and sometimes would show off but it was good to see what we could eventually accomplish at first we didnt like it but he showed us the importance of solving the problem on paper before you even type any code out and it has helped tremensdously in the coding courses

im a recent grad in programming. and i completely failed my first interview. this video helped me so much! i learned so much cause i am one of those over thinkers that writes complicated code making problem solutions more complicated than they have to be.

I think that for problem solving it's also very important to know what actions you can do. For example, in the water problem you can pour from one container to the other. In programming you also need to know what instructions you can do, what commands are available, what APIs you can call, and in general what components/pieces/actions are involved/possible in the problem.

Glad you are enjoying the book. I've got some good puzzles worked out for upcoming videos. Coming soon!

I was so proud of myself when I heard the solution for the permutation problem's solution.... Thank you, this is what I and many other programming learners need.

Who solved the watter puzzle imidiatly if you do thumbs up

The "lesson" or message from this video means you should approach problems for a different angle and interpret it differently. It was not meant to be a video on how to write efficient code. Dont start comment wars please ^^

I had started programming since 3 moths and I found the solution from the first time but I think that what you did in for loop is more more more interesting

My Professor has failed me twice in a TDD exam and when I asked what to do in order to pass his exam, he said I am not a programmer. Thank you for this Playlist. I can't wait for a retake!!!

Thank you for the information, it's a great video. I am learning to program with Python. I consider myself a beginner in programming. Even though, I solved that problem (without looking at the answer) in 5 lines! Now I really understand why so many people prefer Python...

Thank you for the video, it helped me get a clearer picture of how programming needs to be approached. I bought your book and I am going to start reading it RIGHT NOW!

I just recently started to study programming. I'm a very beginner. As you suggested I paused the video and tried to make the department number program. I came up with a solution: I did the same 3 loops you did for your 0-10 permutations: for (int fire=1;fire

This is GREAT. Thank you!

Oh boy did that department problem make my heart skip and beat. I'm watching this to improve my problem solving skills in JavaScript. I am coming from a medical background with JS bring my first language.

Thank you for the video, I am a struggling software engineer who is trying to crack white board interviews and failing miserably. Looking at your videos make me realize that my thinking is right.. I should just fine tune the way I think and believe more in my abilities.

Never programmed before but my first thought was to output all permutations, but them I figured maybe it wasn't allowed, then it turned out to be the solution. Maybe this programming thing will work out for me after all. This video will still be very helpful for me, as other problems have tripped me up in the past.

Im a programmer and I solved both puzzles. I did the second one in java just to test it. These were really nice. I remember when I had to write a piece of code that displayed all prime numbers in an interval without using the modulus operator. Its rather easy but back then I was just starting to code. It was frustrating but once i figured it out I felt so special. LOL

That's funny. My mind jumped to generating all permutations and having an IsValid function while you were describing the problem. But I might include looping the "police" number by 2 and determining the "sanitation" number as forced by the other two as refinements to make the program faster. The most important part is always getting the code to work.

This would be a situation where you could avoid brute forcing by just thinking of all possible number triples. If the PD has to have an even number between 1 and 7, it has to have either 2, 4, or 6. Whatever number it takes, the other two have to have two different numbers that are the difference between it and 12, which result in rather few possibilities. Below is a quick javascript solution. //in each sub array the 0th is the PD, 1st is FD, and 2nd is SD. var permutations = [[2,6,4], [2,7,3], [4,7,1], [4,6,2], [4,5,3], [6,5,1], [6,4,2]]; /*because the above are just all possible number triplets, not all possible permutations... we need to account for the possible permutations of the above triplets fortunately, this just means switching the FD and SD numbers, because the PD's number has to be fixed. This can be done with a for loop, and we'll just tack the results on to our array.*/ for(var i = 0; i

Thanks for giving me the illusion of being a genius by solving this right away. Now let me get back to bagging groceries.

Thank you Anton! Im looking forward to buy your book! This is really great tips you give.

Love this series ...it really gets my brain working as it should got all the problems in few seconds Thanks for making this

Wohoo! I figured it out in like 5 seconds! Never heard of it before btw.

i love this content so much no other channel does this thanks

For the cup scenario, it only took me like 5 seconds. I feel soooo special right now.

when u showed problem i paused video..opened turboC++ and started codding took approx. 20 min to solve it .. i used 3 vari. ...police vari was an array with all possible even numbers and then i put 3 for loops to travel all possible sequences ..finally in the center i put if condition like (all vari should equal and sum==12).. gave multiple solutions on console..! tx 4 brainteaser :D ...

I made the it in small basic and the total outcomes were 14, although that wasn't the problem: For p = 2 To 6 For f = 1 To 7 For s = 1 To 7 If p + s + f = 12 And (p/2)-Math.Round(p/2) = 0 and p f And f s And p s Then TextWindow.WriteLine("police "+p) TextWindow.WriteLine("fire "+f) TextWindow.WriteLine("Sanitation "+s) outComes = outComes + 1 EndIf EndFor EndFor EndFor TextWindow.WriteLine(outComes)

There are thousnds of tutorails on learning various languages and frameworks.... but this series , i dont even need to mention it... thank you

Becoming a programmer is first recognising you have a great need for this type of thinking . It’s like my brain need to lift som weight before I can flex and solve these problems

Wow, I've always been good at puzzles and riddles, but programming made me feel like I was a 2 year old trying to jam a square block in a round hole. I had no idea how to turn my solution into code without just doing it by rote. I've been working with programmers in software for over 10 years... I can come up with "code" in my head and when I explain it to programmers I work with they can make it work...but I couldn't do it myself and I really wanted to be better at that! Thank you so much for this, I will definitely be buying your book!

Finally, a video that answers the real challenge of programming.

Saw the puzzle for fist time and solved it almost immediately. I think 90% CAN solve it not a few!

I am thinking like a programmer already. Got the water challenge at first glance. Maybe its cos i studied science at school, and did this whenever i did not have the right measuring beaker....... But the second problem. That requires serious programming. Thanks Anton

These are cute little problems illustrating a whole bunch of important points. The measuring problem is fun to follow with an “exercise”: solve the same problem but with a 6 oz instead of 5 oz. The modified problem looks similar but has no solutions (see Diophantine equations). Thus, it is important to distinguish a general case from a particular given situation. Hence, there may be the need for finding out, if we’re in a good or bad situation. The enumeration problem brings about many contexts: from the 3-partition problem, to various linear and nonlinear programs. An important lesson: don’t fall into the trap of premature optimization. What if the next year another departments, say, building and finance, are added. And the whole enumeration thing must be done in literals (county started to comply with state’s recommendations) but no combination of chosen literals may contain a reserved word with the list of the words provided. Good video!

I solved the first puzzle in a few seconds, but once you started emphasize the difficulty I had to go back and ensure I understood the problem correctly. My first solution was the right one. The second puzzle was quickly solved too. I'm a programmer.

My program using Python: def main(): for fir in range(1, 8): for pol in range(2, 8, 2): for san in range(1, 8): if fir != pol and pol != san and fir != san and (fir + pol + san == 12): print(f"Fire: {fir} - Police: {pol} - Sanitation: {san}") return 0 main() Not the best-optimized code, but it just works with 14 permutations as the result.

this is saving my life right now thank you!!

My take away is "Take a holistic view of the problem first and keep all options open" and avoid confirmation bias as well

Sir , please continue this.This is really helpful

start with this: , then in another loops for other dept. skip that policeNum to reduce iteration count

These videos are a great compliment to the book. I am very happy with my purchase. Thanks V. Anton Spraul.

V. Anton Spraul, thank you!

Damn that's probably the least optimal solution! Try checking the necessary conditions at each loop and break if they are not met.

Currently, eating the book it's an amazing book I have a bachelor's degree in computer science and informal system but your book is super awesome 🌟

It was actually pretty simple. I just did the main loop with the police department at 2, 4 and 6, then I nested two more loops for the fire and sanitation departments. In the second nested loop, I checked to see if both the total equaled 12 and if the fire and sanitation departments didn't equal each other - you don't have to worry about either one being equal to the police department. Then displayed all those that passed the if statement. Mind you, I haven't watched what his solution is yet so I'm not sure what he did in the video to solve the problem.

Been programming for a little lest that 6 months. I did it my own way(little longer than your code) and these where the results: 1-5-6 1-7-4 2-4-6 2-6-4 3-5-4 3-7-2 4-2-6 4-6-2 5-1-6 5-3-4 6-2-4 6-4-2 7-1-4 7-3-2 Oh and I remember the water question, our lecturer gave us that on the first day of class. I never figured it out. Six months latter this video shows up on my homepage and instantly figured out the question when I saw it LOL

So pumped that I was able to solve the last one! Thanks!

Those were not permutations, but variations. Permutations are something different, like if you have 3 peedifined digits, you can form 3! = 6 different numbers out of them (if you must use all of them exactly once). If you can use any digit and you can use it more than once, then you can form 10^n (in our case 10^3 = 1000) numbers. That is called the variations.

The first problem was so simple, i can’t believe I didn’t get it immediately lolol I had identified that the difference between the two cups was exactly what was needed so I had thought just fill an empty 3oz cup with the 5oz cup over a pan, and the spilt over water should be collected which should equal 2oz

I totally had the wrong idea with the measuring cup problem lmao. I though "well if you fill up both measuring cups to the max, place the 5 oz cup inside a bowl, and pour the 3 oz into the 5 oz: the displaced water will be exactly 2 oz"

I've written last permutuation problem in different approach in python. Please check anyone if I'm right or wrong. Please correct if i'm wrong :) for police in range(2,7,2): for fire in range(1, 8): for sanitation in range(1, 8): if police + fire + sanitation == 12: print(police, fire, sanitation) Here, police should be in even so initially I've looped from 2 to 6 in interval of 2, (So i don't need to worry about even number of police) within that loop I ran another for loop for fire, and within those both loops I ran another for loop for sanitation, and at last I'm printing only those values whose sum is equal to 12 Total permutuations: (Police, fire, sanitation) 2 3 7 2 4 6 2 5 5 2 6 4 2 7 3 4 1 7 4 2 6 4 3 5 4 4 4 4 5 3 4 6 2 4 7 1 6 1 5 6 2 4 6 3 3 6 4 2 6 5 1

It's 5am and I haven't slept but the water puzzle was easy as shit. Instantly got it.

Maybe the first problem with the two cups is considered difficult, because the first example shows that both cups are already filled. If only the 5 oz. cup were filled, and the 3 oz. is shown as being empty, more people should instantly arrive at the solution: 1: 5-3 = 2 2: Pour water from 5 oz. to 3 oz. cup 3: Leaving 2 oz. of water in the 5 oz. cup Also the second example in which the problem is restated, for some people it ends up being difficult. They would remain being unable to see that pouring fluid from the 5 oz cup into a filled 3 oz cup to arrive at 2 oz remaining in the 5 oz. cup. The reason is that, when given a problem such like this, people tend to think that they aren't allowed to empty one cup, or pour liquid from one into the other. Specifically when there is no mention that such things are allowed in the problem description people wouldn't even consider doing it. Which makes an utmost simple problem a big thing. Would the description say, or the problem be given as: "You have a 5 oz. cup filled with water, you have an empty 3 oz. cup. You wish to measure exactly 2 oz. How are you going to do it?" instead of showing an additional example where both cups will be filled? It is simple maths that 5-3 is 2. And if one 5 oz. cup is filled, the other left empty, and you wish to arrive at 2, there is only one simple way to get there. ;-)

Just bought the book.. hope that being from 2012 that it still works.. not for C++ but for understanding the mind set

okay! thanks for ideas but that water puzzle was common for me and once again thanks a lot Hope you will share more puzzle coming days

very instructive! I do really benefit from it!

That was a great approach. Thank you very much.

I think there is something wrong with the puzzle, the aim is not to get 2oz (seriously there is nothing to think about). The puzzle is to get 4oz with 5oz and 3oz. Much less straight forward. Here is the answer: fill 5 fill 3 with 5 => 2 left in 5 empty 3 => 0 left in 3 put the 2 left from 5 in 3 => 2 in 3 fill 5 => 5 in 5 fill 3 with 5 => 4 in 5

I assumed both jars were filled. I poured half of the water out of the 3oz jar leaving only 1.5oz. I then fill the 3oz jar back to 3oz from the 5oz jar of water leaving 3.5oz of water in the 5oz jar. I repeat the process again and that leaves me with 2oz of water in the 5oz jar and 3oz of water in the 3oz jar. This all works if I'm allowed to eyeball what I think to believe is half of the water left in the 3oz jar. But eyeballing half is pretty close in general, so I believe this should work. But if I knew only the 5oz was full and the 3oz jar was empty that would have been a no brainer addition and subtraction problem.

This video is very helpful and in the same time exciting 👍🏻

Thanks for the comment. Problem solving develops with practice, like any other skill. My book has lots of exercises to work through. If you can't get your hands on it, my next video may give you some ideas on developing your own exercises.

I would recommend to delimit your dataset. It is not only (way) faster, it makes the code more readable and allows you to actually solve complex problems. Programming is not about adding valid data; It's about subtracting invalid data. The code in this video (10:40) smells. JS approach: for (var i=1; i

python approach :) for x in range(1,8): for y in range(1,8): for z in range(1,8): #If even number if z % 2 == 0: #If there aren't any duplicates if len(list(set([x,y,z]))) == 3: #If all add to 12 if x + y + z == 12: print "Police: {0} Fire: {1} Sanitation: {2}".format(z,y,x)

My solution in Python 3 for the problem. It comes back with a solution of 17 permutations: num_list = [] for fire in range(1, 8): for police in range(2, 8, 2): for sani in range(1, 8): if fire + police + sani == 12: num_list.append((fire, police, sani)) print(len(num_list))

The riddle (10:40) would have been more interesting, if the police dept (i) only wanted odd numbers. You wouldn't have to check, whether the fire / sani dept have the same number, because the sum (12) minus any odd number (i) would always result in an odd number, that cannot consist of two times the same number. for (var i=1; i

Your book is a life saver

my thoughts on the water puzzle was to pour the two full containers into an unmarked container, then scoop it out with the 3 ounce cup, and the remainder is 2... i was close :P

Extremely helpful! Will consider buying your book :)

One-liner in Python: print ' '.join(map(lambda x:'{} - {} - {}'.format(*x),filter(lambda x:(len(x)==len(set(x))and sum(x)==12 and not x[1]&1),((a,b,c)for a in range(1,8)for b in range(1,8)for c in range(1,8)))))

Nice video, but very inefficient way of solving the task. Time complexity is O(n^3). You are doing 7*7*7 iterations. You can reduce number of iterations by 4/7th's if you put policeDeptNum % 2 == 0) in the outer loop... And since you know that (12 - policeDeptNum - fireDeptNum = sanitaryDeptNum) you don't need the third loop. I was able to find all 14 solutions doing no more than 27 iterations.

And I start geeking out over ham and Swiss and Swiss and ham lmao

a great help for a BSIT student like me..😁👍👍 thank you sirrr

i need more of this... thanks a lot

Great tutorial. I was really suprised at the simple solution to the last problem :) I am reading your book, loving it so far. You should do more tutorials on puzzles like the last one in the video!

Speaking as a programmer with over 40 years of experience, I find it too bad that the final solution he came up with was the most inefficient--discarding some of the optimizations that he'd already discovered. For example, it would still be valid to calculate the sanitation number by subtracting the sum of the other two numbers from 12, thus eliminating the innter loop. It would also still be valid to force the police department to be even, as he did in the earlier attempt. Part of "thinking like a programmer" is not being satisfied with the first solution that works. It is often worthwhile to re-examine your solution to see how it can be optimized. If you're writing production code that might be used thousands and thousands of times, it's not only worthwhile, it's vitally important. And--don't casually discard your earlier thoughts--they may still have value.

An if statement checking for the correct answer was the first thing I thought of because I like to debug incorrect answers by seeing why they are incorrect. It's kind of a faster way to do trial and error. Also, for the cup problem, you used the wrong number; you're supposed to make 4 ounces of water, not 2.

The permutations of the Department numbers are as follows: 147. 165. 246. 264. 327. 345. 426. 462. 507. 543. 561. 624. 642. 705. 723. 741.

I have no experience with Programming whatsoever so I have no idea how this would be executed however I thought for the Dept problem the police number would always be 2,4 or 6 for each of these the sum of the other two has to be either 10, 8 or 6 I wonder if a loop could be coded only for numbers to add to those quantities and be different from one another

Very helpful videos! Thank you!

import itertools a = [x for x in range(1, 11)] permutations = itertools.permutations(a, 3) for p in permutations: if sum(p) == 12 and p[1] % 2 == 0: print(p) I did this, not sure if it's right

Funny, I came up with something like: tot = 12; maxNum= 7; for (p = 2; p

Programming comment threads and forums always remind me that fundamentalism is everywhere and that just because someone knows how to write code does not mean they understand what it means to be a scientist. I'm not a scientist, but I do think ethics and experimenting are more important than how smart you think you are. EDIT: My first solution was to simply count by twos and subtract 7 from the counter to get all permutations. Then I just looped through the result to find the one that satisfied the police chief's non-primacy law and the sum-to-twelve requirement.

Here is what the program looks like written in Python 3 for i in range(7): if (i+1) % 2 == 0: #i will be Police so this is to check if the number is even, the +1 is due to the fact the loop starts at 0 for j in range(7): if j != i: # checking to make sure j isn't equal to i for k in range(7): if k != i and k != j: #checking to make sure k isn't equal to j or i if i + j + k + 3 == 12: #checking if the sum is equal to 12, again the +3 is due to the fact counting starts at 0 print(i + 1, j + 1, k + 1) #if everything passes print the numbers

I did this in Python. I wrote it on paper first to figure it out then did it on the computer. I made a mistake that made it so 4 solutions were cut off because I accidentally didn't include 7 in my possible numbers. Other than that it worked on my second try. I think the way I did it might be slightly more optimized because it checks if the number is valid before it goes on to generating the next number so each preceding for loop has to run once less instead of having to run 399 loops. It only has to run 154 loops.

The Department Number Permutation can be solved with only one loop. O(n). Just try solving it by getting total number of permutations by 7 raise to power 3. You will figure out the rest yourself.

Simply statistics would help a lot with the generation algorithm. No repeating numbers means there are 7x6x5 possible arrangements, so that's your for loops right there. The rest is straightforward

Great video, thank you very much!

Ordered your book today!

This is how i solved problem with getting 2 ounces of water: 5\2=2.5 and 2.5\2=1.25 than 3\2=1.5 and 1.5\2=0.75 the solution is 1.25+0.75= 2 I feel i little dumb however, when you shoved you approach it seemed so obvious that i asked myself how couldn't i see it?

Your solution is good, but it can get simple optimisation aka you could at least do the police departament to be even always and not generate the sanitary, just check if the sum is < 12 in wich cas us true the sanitary becomes the remaining part and then check the if they are different. Way faster( 2 less checks for each posible combination and not generating a third value and generating 3 police values instead of 4. Further optimisation is posible but imma not go into details.

SO FUCKING AWESOME ! THANKS for the book and videos! That is what I were looking for all the time! Greets from Slovenia.

Thanks man !

Hi! I am an optimizing compiler. I will now parse your puzzle: "If you have a 5oz cup and a 3oz cup, how do you get 2oz of water?" Whoops! You have invoked undefined behavior. Guess it's up to me to re-interpret your question. As it's not specified whether or not the two cups are filled before I can begin solving the puzzle, I can assume it's impossible for the cups to transfer any water. Thus they must be immovable. As immovable objects are an impossibility, your cups must not exist, therefore, I can delete some text here and there, and optimize your puzzle to just: "You have 2oz of water." I will now attempt to answer this puzzle: If I have 2oz of water, then I have 2oz of water Answer: yes

My solution whould've been. Loop police first. Then fire from 1 to (7 or police + fire = 11). Then sanitation = 12- (police + fire). With "then" I ofc mean that it's inside the previous loop mentioned.

I solved the department program extremely quickly :D I love problems like this, make the computer do the generating and make it check it too, no need to manually check :P