#Help I'm stuck with this exercise bird watcher

1 messages · Page 1 of 1 (latest)

dense crown
# 
export function birdsInWeek(birdsPerDay, week) {
  let total = 0;
  for(let i = 0; i < birdsPerDay.length; i++) {
    total += birdsPerDay[i];
  }
  return total;
}

I have read the exercise many times, but I cannot understand it well. What makes it difficult for me to start.

2 task: Now that you got a general feel for your bird count numbers, you want to make a more fine-grained analysis.

Implement a function birdsInWeek that accepts an array of bird counts per day and a week number. It returns the total number of birds that you counted in that specific week. You can assume weeks are always tracked completely.

mortal stag
#

The array birdsPerDay contains counts, one per day, that represent how many birds have been spotted on that particular day.
For example: birdsPerDay = [2, 5, 0, 7, 4, 1, 3, 0, 2, 5, 0, 1, 3, 1]; means that in the first week you've seen 2, 5, 0, 7, 4, 1, and 3 birds (seven days per week), 22 in total. In the second week you've seen 0, 2, 5, 0, 1, 3, and 1 birds, 12 in total.

For task #2 you're supposed to implement the function birdsInWeek that gets as parameters the array birdsPerDay and the number week. You have to calculate how many birds you've seen in that specific week.

#

Do you understand the example?

birdsPerDay = [2, 5, 0, 7, 4, 1, 3, 0, 2, 5, 0, 1, 3, 1];
birdsInWeek(birdsPerDay, 2);
// => 12
dense crown
#

I understand but I am confused by the fact that I have to take into account the index of the beginning and end.

mortal stag
#

How would you as a human perform this task if I gave you that array above and asked you about the number of birds in week 2?

dense crown
#

I don't know, it depends on how many weeks it is, if it's week 2, then week 1 shouldn't count.

lethal cedar
#

What @mortal stag asking you is if you have a physical calendar of a month start from day 1, each day has a number of birds on it. How would you count the sum when he asked you to start counting only bird for the 2nd week.

dense crown
#

I would count from 7

lethal cedar
#

You are on the right track. What if he ask for 3rd week?

dense crown
#

14

lethal cedar
#

Right, so you recognize that there is a pattern for the starting day, yeah? Depend on the asking week

dense crown
#

Yes

lethal cedar
#

So now you can apply that logic, you find the start counting day (the index) , and then you count for a week.

dense crown
#

I'm thinking how to apply it

lethal cedar
#

Think of how you usually start a loop from a -> b. Like counting from 0 to 10, start from 0 and increment 1 by 1 to 10. But this time, the starting point is not a fixed 0, it is a dynamic value based on the input of the week in focus

dense crown
#

I understand, but if it starts with a dynamic variable, that is, with a week, and it has to count from 7, I don't understand how to do it.

#

I have to make it start at the number that ends the week, that is, like a range

lethal cedar
#

Week 1: ?
Week 2: 7
Week 3: 14
Week 4: ??
Week 5: ??

If u can fill this out and see the pattern, then you can get the starting day value.
Hint: it related to how many days are in a week

dense crown
#

Week 1: 1
Week 2: 7
Week 3: 14
Week 4: 21
Week 5: 1

lethal cedar
#

oh yeah my bad i should clarify that in this case we dont use normal calendar anymore, it is just a long year of weeks. so week 5 shouldnt wrap around and be 28 in your case

#

if week 1 start at day 1, would week 2 start at day 7?

dense crown
lethal cedar
#

If monday was start day aka day 1, what day is next monday?

dense crown
#

But I can't think that starting at 7 would be 1 and then do the counting again.

timid spindle
#

What would the last day be for weeks 1, 2, 3?

dense crown
#

My head doesn't work hahaha

timid spindle
#

7 for week 1? What about week 2? And week 3?

dense crown
#

I'm thinking as if it were a range, 1 week is 7, but if it's 3 weeks it would be 21

timid spindle
#

What is the start index and end index for week 1, week 2 and week 3?

# 
Week 1:  <start> - <end>
Week 2:  <start> - <end>
Week 3:  <start> - <end>
dense crown
# 
Week 1:  1 - 7
Week 2:  8 - 15
Week 3:  16 - 23
timid spindle
#

Is day 7 part of week 1 or week 2?

#

Is day 15 part of week 2 or week 3 😄

#

Week 1 is 7 - 1 = 6 days long. Week 2 is 15 - 8 = 7 days long. Week 3 is 23 - 16 = 7 days long.

#

Well. I did math wrong, since those ranges are inclusive.

dense crown
#

Why 6?

timid spindle
#

Week 1 is 1..7 = 7 days long. Week 2 is 8..15 = 8 days long. Week 3 is 16..23 = 8 days long.

#

The end - start should be the same for all weeks.
Week 1: 7 - 1 = 6. Week 2: 15 - 8 = 7. Week 3: 23 - 16 = 7.

#

That suggests your start/end numbers might be wrong:

Week 1:  1 - 7
Week 2:  8 - 15
Week 3:  16 - 23
#

Does that seem right? Do you see the issue?

dense crown
#

I do not see the problem

timid spindle
#

Week 1 is a different length than week 2 and week 3

#

How many days are in 3 weeks?

dense crown
timid spindle
#

Week 1 to week 3 is days 1-23?

timid spindle
#

Try writing out numbers like a calendar

dense crown
timid spindle
#

How many days are in 3 weeks? 23 days?

dense crown
timid spindle
#

How many days are in one week?

dense crown
timid spindle
#

How many days in two weeks?

dense crown
#

14

timid spindle
#

How many days in three weeks?

dense crown
#

21?

timid spindle
#

Pull out a calendar and count 😉

#

What days are in week 1? Week 2? Week 3?

Week 1: start - end
Week 2: start - end
Week 3: start - end
dense crown
cyan silo
#

April 2024 would be a better example...?

timid spindle
timid spindle
# dense crown

No 23 then.
What days are in week 1? Week 2? Week 3?

Week 1: start - end
Week 2: start - end
Week 3: start - end
dense crown
# 
Week 1:  1 - 7
Week 2:  8 - 14
Week 3:  15 - 21
timid spindle
#

That seems more reasonable. Now they are all the same length 😁
And you have that nice pattern of 7,14,21 which matches the days in a week!

#

Do you see a pattern in those numbers?

#

What would be the start and end for week 10?

dense crown
dense crown
timid spindle
#

That makes sense, given that a week has 7 days

#

What's the start and end for week x?

#

Note 70-63=7 which is different from weeks 1,2,3

dense crown
timid spindle
#

What about week=8?
Can you figure out out in terms of a variable, n?

dense crown
#

I can't take my stress anymore

timid spindle
#

Take a break! Try again later.

dense crown
#

Can you explain it to me as if I were 5 years old?

timid spindle
#

If week 1 ends on day 7, and
If week 2 ends on day 14, and
If week 3 ends on day 21, then

When does week x end?

cyan silo
#

or which multiplication table represents this sequence, maybe?

dense crown
#

X, what would it be?

#

1 x7
2 x7
3 x7
4x7

cyan silo
#

you are almost there, can you answer my last question? The pattern you need is in the answer...

timid spindle
#

Exactly!

#

And for week 10?

dense crown
#

10 x7

timid spindle
#

And for week number?

#

Where number is a variable...

dense crown
#

week x 7?

timid spindle
#

Yes

#

Or number * 7 technically

dense crown
#

Okay

timid spindle
#

That gives you the end of any week. Can you do something similar to find the start of any week?

dense crown
#

Yes that's fine

timid spindle
#

If you can find a formula for the start and end of any week, you can use that to get the range of days in any week

#

Which can be used to count the birds in any week

dense crown
# 
let indexEnd = week * 7;
let indexStart = week - 1 * 7;
timid spindle
#

That looks roughly correct

dense crown
timid spindle
#

🎉

austere spearBOT
#

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dense crown