! What do these two diagonal red marks mean in the YouTube app? They are only seen on the videos that I have uploaded page.]1

# Tag: Red

## Need clarification on applying for UK Visitor Visa from a Red list country

The GOV.UK visitor visa advice for applicants from Red list country states that:

If you’re applying for a visitor visa

Your application decision may be delayed if you’re applying from a red list country where travel to the UK is suspended. You’ll receive your visit visa when suspension of travel is lifted if your application is successful.

I am little confused by this. Does this mean my application would be evaluated when the travel restrictions are over *OR* I can apply now and a decision would be made i.e. **visa granted/refusal** but I would not know about the outcome until travel restrictions are over.

Please clarify this to me.

## Synology does not recognize the WD Red Drive in the Storage Manager

I’m trying to upgrade my storage on my NAS. I have purchased two 4TB WD Red Plus for the DS920+. I’ve inserted the first drive which worked perfect and has been recognized by the Storage Manager.

Then, I have inserted the second one and this just starts to do some noises and responds with a kind of error beep.

I have also here a video, what happens when I plugin the hard drive:

Now my question is, if the hard drive is defect or what else this error beep can be?

Thanks in advance.

## probability – A bag contains 6 white balls, 5 black balls and 2 red balls.

A bag contains 6 white balls, 5 black balls and 2 red balls.

If two balls are drawn at random, what is the probability that neither of them are white?

For this question, the method that I used was to consider the four possible cases, BB, RR, BR, RB.

Therefore $$P = P(BB)+P(RR)+P(BR)+P(RB)=frac{5}{13} times frac{4}{12} + frac{2}{13} times frac{1}{12} + frac{5}{13} times frac{2}{12} + frac{2}{13} times frac{5}{12} = frac{7}{26} $$

which gives the correct answer, but I found there are two other ways to do this question, neither of which I understand.

Alternative method 1):

$P = P(text{red/black first pick}) times P(text{red/black second pick})

=frac{5+2}{13} times frac{(5+2)-1}{13-1} = frac{7}{26}$

This obviously kind of makes sense, but I’ve just never seen a question done this way before, I would really appreciate if someone could explain logic behind this in detail, and also point towards some textbooks that explain this part. (I already searched through the textbook I have, but I haven’t seen them use this method in a worked example..)

Alternative method 2)

$$P = frac{{}_5C{}_2 + {}_2C{}_2 + {}_5C{}_1 times {}_2C{}_1}{_{13}C{}_2}=frac{7}{26}$$

What I don’t understand about this method is why we didn’t view BR and RB as two different cases, i.e., why we didn’t do

$$P = frac{{}_5C{}_2 + {}_2C{}_2 + {}_5C{}_1 times {}_2C{}_1 + {}_2C{}_1 times {}_5C{}_1 }{_{13}C{}_2} $$

Thank you so much for the explanation..

## usa – In the US, does a stop sign take priority over a red light?

## monsters – Are Griffin’s red or white meat

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Killed a Griffin in rpg.

This was my first question.

We couldn’t figure it out so I thought I’d ask.

It is important for whether or not we can have griffin steak.

$endgroup$

2

## depth first search – Find palindrome in directed Graph where edges are either blue or red

Here’s a possible algorithm.

Construct a graph $G’$ with $|V|^2$ vertices where each vertex is labeled with the pair $(a, b)$ with $a, b$ being vertices in $G$. Then, construct all possible edges $(a, b) to (c, d)$ in $G’$ where two edges $c to a$ (note the order) and $b to d$ exist in $G$ with the same color.

Then to find an odd-length palindrome you simply check if $(s, t)$ is reachable from any $(x, x)$ in $G’$. To find an even-length palindrome check if $(s, t)$ is reachable from any $(a, b)$ in $G’$ under the condition that $a to b$ exists (regardless of color) in $G$.

The idea is to extend the palindrome from the middle out. The vertices $(l, r)$ in $G’$ represent the leftmost and rightmost symbol in our palindrome, and the way we constructed the edges in $G’$ corresponds to all valid ways to extend the palindrome.

## javascript – Sistema de alertas de temperatura con Node Red

Estoy creando un sistema de alertas que avisa cuando la temperatura supera un cierto rango y que envíe una notificación por Telegram.

La cuestión es que también me debe de avisar cuando el valor haya vuelto al rango normal pero no sé cómo hacerlo.

Por ahora sólo me avisa cuando supera los parámetros (<24 y >17) pero no cuando vuelve a la temperatura normal.

Gracias!!

## Counting the number of comparisons in red black tree

I have an array with $N$ elements and I run an algorithm that find how many distinct elements are in the array by using a red black tree as follows:

- for each element
- if element not in tree
- insert element to tree
- increase distinct elements counter by 1

- if element not in tree

I need to find a formula to count how many comparisons the algorithm performed with $N$ as variable for both the best case and worst case.

For the best case this is pretty easy, the array include $N$ instances of the same element so each search does 1 comparison and there is no insertions, except for the first element, hence the number of comparisons is $N-1$.

But I’m having trouble with the worst case. Firstly I’m not sure what is the worst case in this scenario as red black tree balance itself after each insertion, I do know that all the elements in the array must be distinct but in order to get the worst case I will need that each search will go down the longest route to a leaf and same with the insert. How can i devise an input array that cause the worst case and how to create a formula that calculates the max number of comparisons?

## python – Visualization with Folium – instead of bubbles on map i get whole screen painted in red

I’m going to make fast visualization project with Python/Folium but, I’m stuck in an awkward situation. Note: I’m using Jupyter Notebooks.

Here is my code:

```
import folium
import pandas as pd
map = folium.Map(location=(44.80401, 20.46513))
folium.TileLayer('cartodbpositron').add_to(map)
```

And small data frame:

```
data = pd.DataFrame(
{'lon': (20.303479, ..., ...),
'lat': (44.482519, ...., ...),
'name': ('...', '...', '...'),
'value': (54196, ..., ...)}, dtype=str)
```

…but when i execute following code:

```
for i in range(0,len(data)):
folium.CircleMarker(
location=(data.iloc(i)('lat'), data.iloc(i)('lon')),
popup=data.iloc(i)('name'),
radius=float(data.iloc(i)('value')),
color='crimson',
fill=True,
fill_color='crimson'
).add_to(map)
map
```

I want circles/bubbles with radius similar to value from data frame, but i got this.

Screen after executing code for visualization via Folium

Cant even scroll, there is red color over the whole map window. Cant figure whats wrong, thank you in advance!