The Father-Son duo's story - the four layered nested vectors...

My school going son, Ridit, had a complain against me...

"Baba, why didn't you teach me about nested vectors earlier? I am stuck in a particle simulation application where i am using Incremental Potential Contact (IPC) for collision detection. And I am trying to decipher the 4 layered nested vectors now."

" Okay... It's a little difficult for new comers. That's why i didn't touch nested vectors when i taught you C++. But here we go..."

1. Vector of Character: The String

"Look at your name: 'R-I-D-I-T'," I said, writing it on a whiteboard. "Each letter is a single character, right? A computer takes those individual characters and lines them up, one after the other, to make a single word."

"That single line of characters? That's what we call a 'vector of character'. It's the simplest type, just like a single word. And you know its called a string... right!!!"

Ridit nodded... Yes...

2. Vector of String: The Family Member List

"Exactly! Now, let's take a step up. You, me, and Mom." I wrote:

• Ridit

• Dad

• Mom

"See? Now we have three separate 'strings'—three names. A computer can take a whole list of these strings and put them together into a bigger list."

"That bigger list—the list of names of all our family members—is a 'vector of string'. It's like a single list where every item is a word or a phrase. It’s a list of words."

3. Vector of Vector of String: The Family Album

"Now, let's think bigger. Imagine your friend Ishan's family. They have their own list of names, right? Ishan, his mom, his dad."

I drew a box around their family's list and another box around Ishan's family's list.

"In our program, we could have one list for The Sharma Family and a second list for The O'Connell Family. We now have a list of lists of names."

"That's a 'vector of vector of string'. It's an organized list where each item is a complete list of names from a different family. It's how we organize data for something like a Family Tree app or a guest list for a big party, where you group guests by family."

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4. Vector of Vector of Vector of String: The Global Directory

"Alright, last one, the biggest level. Imagine a program that keeps track of families all over the world. Our set of families is in India." I wrote 'INDIA' above the Sharma and O'Connell families.

"Now, there's another set of families living in Japan , and maybe another set in Brazil."

"We can take the entire collection of Indian families (our previous 'vector of vector of string'), and put it on a larger list next to the collection of Japanese families and the collection of Brazilian families."

"This final, massive list is a 'vector of vector of vector of string'," I finished, pointing to the largest, outermost box. "It's how we group data by a major category, like Nation. It's a huge directory where each entry is a list of all the families in a specific country, and each family is a list of all its members."

Here's a pictorial explaining the above concepts ...

I told my son...Computer Science is like studying different seemingly disconnected subjects together.... but when the convergence happens after years of experience, the bigger picture comes out.

Then I asked my son, could you map this kinds of Data Structure with any of the design pattern you studied?

"Yeah... Composite Design Pattern...", Ridit answered confidently.

"Good... ", i said. " Now finish your particle simulation and contribute to the body learning of the universe. That's our final goal..."