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[Avis-Mergulus]

Avis-Mergulus:
What does it say you messed up with?

"Incorrect answer", so at least it didn't crash. I have no way of knowing what was in the tests, though.

[Skyrunner]

I'm using Selenium to scrape my university's antique, dynamic, non-restful, "secure" course finder (ie, a part of the site that DOES NOT NEED AUTH)...

It's so horrible, yet I keep finding parts that are even more horrible. I don't even, anymore

this HTML code is for this:


look upon these works, ye mortals, and despair

(yes, that is a span within a td within a tr within a table within a td within a tr within a table just for kicks)
(yes, they used a '$' in a CSS selector)
(nothing like 'win0divNYU_CLS_DTL_CLASS_NBR$1' to brighten up your CSS)

edit: "table>tbody>tr>td>table>tbody>tr>td>table>tbody>tr>td"

[strawberry-wine]

this HTML code

I wonder which elder god they hired to design that

[Telgin]

I sincerely hope that those selectors are automatically generated by something.  Some kind of application framework, probably.

I've only had bad experiences with full stack application frameworks...

[Mephisto]

It's university software. It's a given that the code will be bad.

It may also date from a time during which table-based layouts were the shiz.

[Gatleos]

Spoiler (click to show/hide)

while (userChoice == compChoice || userChoice <= 0 || userChoice < 4){

      cout << "You have either tied the game or it is now restarting due to incorrect input." << endl;
      cin >> userChoice;
      compChoice = ((rand() % 3) + 1);

      if (userChoice == 1 && compChoice == 2){
         cout << "Your opponent picked: " << compChoice << endl
            << endl << endl;
         cout << "You lose" << endl << endl << endl;
         //user rock comp paper
      }

      else if (userChoice == 1 && compChoice == 3){
         cout << "Your opponent picked: " << compChoice << endl
            << endl << endl;

         cout << "You win!" << endl << endl << endl;
         // user rock comp scissors
      }
      else if (userChoice == 2 && compChoice == 1){
         cout << "Your opponent picked: " << compChoice << endl
            << endl << endl;
         cout << "You lose!" << endl << endl << endl;
         //user paper comp rock
      }
      else if (userChoice == 2 && compChoice == 3){
         cout << endl << "Your opponent picked: " << compChoice << endl
            << endl << endl;
         cout << "You lose!" << endl << endl << endl;
         //user paper comp scissor
      }
      else if (userChoice == 3 && compChoice == 1){
         cout << "Your opponent picked: " << compChoice << endl
            << endl << endl;
         cout << "You lose!" << endl << endl << endl;
         //user scissors comp rock
      }
      else if (userChoice == 3 && compChoice == 2){
         cout << "Your opponent picked: " << compChoice << endl
            << endl;
         cout << "You lose!" << endl << endl;

         //user scissors comp paper
      }

   }

Like so? Not going to lie this program is making me smile in frustration and i'm going to be asking how to do this again next class.

That's exactly what people were referring to when they said repeating code fragments is bad. The first thing to wrap your head around when figuring out how programming works, and it can be a little difficult at first, is how to abstract out repeated instructions. Computer programs, especially big ones, spend a lot of time doing things over and over. Your job is to figure out a concise way of telling the computer what you want it to do, so you don't have to copy-paste those same commands again and again. Doing boring, repetitive things is the computer's job, not yours.

The first thing I would do when writing this program is define something like this at the top of the file:

Code: [Select]

const char* options[] = {"Rock", "Paper", "Scissors"};
This is an array of strings, containing the names of the choices the player could make ("const" just means you can't change it on accident later on). Why would we create this? Well, now we can do something like this further down:

Code: [Select]

compChoice--;
cout << "Your opponent picked: " << options[compChoice] << endl;
I'm assuming you exit the loop immediately if the user selects 0, otherwise the program would crash here due to accessing array index -1. Next, we need to abstract out the information that tells us whether the player won or not. How do we do that? Well, we could do it algorithmically, but there's so little information here that we can get away with just defining it the same way we did before. So let's add a second data definition that looks like this:

Code: [Select]

const char* options[] = {"Rock", "Paper", "Scissors"};
const int beats[] = {2, 0, 1};
Okay, lemme explain this. This is another array (of numbers this time), and it tells us what beats what. The number at a given index tells us what the choice at that index beats. So, for example, at index 0 in the array we have the number 2. This means "option 0 beats option 2". Look at the names above, and we see that that's true: Rock beats Scissors. Next, we have "option 1 beats option 0". Paper beats Rock. Last, we have "option 2 beats option 1". Scissors beats Paper.

So, now we can add a block further down like this:

Code: [Select]

compChoice = rand() % 3;
if(beats[userChoice] == compChoice) {
cout << "You win!" << endl;
}
else if(beats[compChoice] == userChoice) {
cout << "You lose..." << endl;
}
else {
cout << "Draw" << endl;
}

Now you have all the logic you need to tell if the player won or not, and your program is about one tenth of the size it was before. I think I need to start listening in history class now, so I'll let you try to figure this out. Let me know if you have any questions.

(Note that compValue is set to a value between 0 and 2 here, whereas in your version it was 1-3)

[Reelya]

That's a pretty cool idea for the "beats" array.

Code: [Select]

compChoice = rand() % 3;
if(beats[userChoice] == compChoice) {
cout << "You win!" << endl;
}
else if(beats[compChoice] == userChoice) {
cout << "You lose..." << endl;
}
else {
cout << "Draw" << endl;
}
But you inverted win and lose here. If the user chooses "0" (Rock), then beats[userChoice] == "2" (Scissors). You then have that if the computer picks "2" (Scissors) then the program prints "You win". i.e player (rock) beat computer (scissors).

If you write out the logic checks in the other order it's clearer what's happening, because the logic reads closer to English word order, which reduces the chance of getting confused (obviously set up the array correctly for this):

Code: [Select]

compChoice = rand() % 3;
if(compChoice == beats[userChoice]) {
cout << "You lose..." << endl;
}
else if(userChoice == beats[compChoice]) {
cout << "You win!" << endl;
}
else {
cout << "Draw" << endl;
}
Now, it reads as almost-English: "if compChoice beats userChoice print you lose" and "if userChoice beats compChoice print you win".

[Avis-Mergulus]

Code: [Select]

def count_matrix(matrix, query):
    matrixFragment = matrix[query[1]-1:query[3]]
    count = 0
    for line in matrixFragment:
        count += sum(line[query[0]-1:query[2]])
    return count
   
initText = open('input.txt')
Lines = initText.readlines()

param = list(map(int, Lines.pop(0).split()))
matrix = [x.split() for x in Lines[:param[0]]]
matrix = [list(map(int, x)) for x in matrix]
queries = [x.split() for x in Lines[param[0]:param[0]+param[2]]]
queries = [list(map(int, x)) for x in queries]

for query in queries:
    print(count_matrix(matrix, query))


So I figured out what was wrong here, but now it's a little too slow. I always have trouble with optimization because I generally have little idea what's fast and what's slow, so what exactly is the slowest part in my code here? The generators or the looping sum thingy? Would substituting the array of arrays with a non-nested array and some index trickery be faster?

[MagmaMcFry]

Now, it reads as almost-English: "if compChoice beats userChoice print you lose" and "if userChoice beats compChoice print you win".

Clearly there is a naming problem here. You can interpret beats[userChoice] either as "what userChoice beats" or as "what beats userChoice". As good programming practice I suggest encapsulating the whole thing in a two-argument function: int winner(int choice1, int choice2), that returns 1 when choice1 wins, 2 when choice2 wins, and 0 for a tie.

[Reelya]

Another way would be to make choice an object and have a "beats" method.

if(compChoice.beats(userChoice))
{
    // you lose!
}

is pretty unambiguous. But i guess if you have a "pick winner" function then you can do a switch statement instead of if statements

[TheBiggerFish]

Why would you make compChoice an object?  That seems rather unnecessary for RPS, guys.
We do not need 100 lines of code to print "Hello World".

[miauw62]

Yeah, making it an object is probably overkill. It works as a demonstration of how to solve other problems, obviously, but a big part of programming is finding the best tools for a job.

[Reelya]

But in this case, it would literally be only a few extra lines of code

struct choice
{
    int val;
    bool beats(val2) { return val == beats[val2]; }
}

making a struct hardly breaks the bank with complexity. it's basically the same overhead as making a function, except nobody ever goes "whoa, cool down with making the functions, you're over complexifying things!"

[TheBiggerFish]

But in this case, it would literally be only a few extra lines of code

struct choice
{
    int val;
    bool beats(val2) { return val == beats[val2]; }
}

making a struct hardly breaks the bank with complexity. it's basically the same overhead as making a function, except nobody ever goes "whoa, cool down with making the functions, you're over complexifying things!"

Weeeeeelllllll.
You can probably have someone do that.

[nogoodnames]

We are talking about a school project here. Introducing new concepts that haven't been covered in the class probably isn't helping.