Sai jayadeep

curious learner
machine learning, mathematics, finance, problem solving,game theory

[Sai jayadeep @Saijayadeep7]

When you double-click an application, what happens step by step inside the computer?

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 19 – What is a queue?

What it is:
A waiting line for work to be done later.
Why it exists:
Systems can’t handle everything at once.

Tiny example:
Orders wait before being processed.
Mental note:
Queue = absorb spikes, smooth load.

[Sai jayadeep @Saijayadeep7]

DAY 19
simple logic is any bracket just before the closing bracket should be the same type if not return false ,That's it

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 18 – What is a bottleneck?

What it is:
The slowest part of a system.
Why it exists:
Systems move at the speed of their weakest link.

Tiny example:
Fast app, slow database.
Mental note:
Optimize bottlenecks, not everything.

[Sai jayadeep @Saijayadeep7]

DAY 18
Could able to solve only one question in the contest and second one is TLE only brute force worked

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 17 – What is load?

What it is:
Amount of work hitting a system at the same time.
Why it exists:
Users don’t arrive one by one.

Tiny example:
Many people ordering food at 8 PM.
Mental note:
High load stresses weak system parts

[Sai jayadeep @Saijayadeep7]

Day 17
Stack vs queue
- a stack is a last in first out LIFO
- queue is a first in first out FIFO
- for ex if you take a box and places plates in order 1,2,...10 . And now the very first plate you take is 10
this is stack
- the exact opposite is queue

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 16–What is throughput?

What it is
How much work a system finishes per unit time
Why it exists
Speed alone doesn’t tell capacity
Tiny example
Checkout system handling 1,000 orders per minute
Mental not
Latency=how fast one request is.Throughput=how many total

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 15 – What is bandwidth?

What it is:
How much data can move at once.
Why it exists:
Links have limits, not infinite capacity.

Tiny example:
Slow video on weak internet.
Mental note:
Bandwidth = volume, not speed.

[Sai jayadeep @Saijayadeep7]

Day 16 – Change Representation When Stuck

Gym drill:
If direct thinking fails, change how data is represented.

Examples:
• values → differences
• numbers → frequencies
• indices → prefix sums
• operations → states

[Sai jayadeep @Saijayadeep7]

Day 15 – Think in “Constraints First”

Gym drill:
Before thinking of logic, read constraints only.

If N ≤ 100 → brute force possible
If N ≤ 2e5 → O(N log N) or O(N) only
If values ≤ 1e9 → watch overflow
If multiple queries → precomputation needed

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
DAY -14
What is latency
-It is a time a request takes to get response
-Data must travel and proceed

[Sai jayadeep @Saijayadeep7]

Day 14 – Resetting how I learn CP Realization: Posting concepts without struggling on problems is useless. New rule: Problems first. Confusion first. Insight later. Goal: Each post should come from being stuck, not from theory. Mental note: Insight sticks only after friction

[Sai jayadeep @Saijayadeep7]

KEEP GOING

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 13 –NETWORK

What it is:
A way for computers to connect and talk to each other
Why it exists:
One computer alone can’t serve everyone

Tiny example:
Your phone sends a message to a server over the internet
Mental note:
No network→no communication btw systems

[Sai jayadeep @Saijayadeep7]

Day 13 – endl vs '\n' (C++ I/O Trap)

Concept:
endl flushes output buffer every time.

Problem:
Frequent endl → slow I/O → TLE.

Fix:
Use '\n' instead.

It helps to reduce the time of the operation

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 12 – Stateful system

What it is:
A system that keeps memory between requests.
Why it exists:
Some actions need context from the past.

Tiny example:
Shopping cart remembers added items.
Mental note:
Stateful = past affects the next step.

[Sai jayadeep @Saijayadeep7]

Day 12 – unordered_map reserve() (CP Trick)

Concept:
unordered_map rehashing is expensive.

Problem:
Frequent inserts → rehash → TLE.

Fix:
mp.reserve(n);

Example:
unordered_map<int,int> mp;
mp.reserve(n);

Used in:
Prefix sum + map,
Frequency counting,
Hash-based solutions.

[Sai jayadeep @Saijayadeep7]

Day 11 – Custom Sort (Comparator)

Concept:
You can control how sorting happens.

Example:
sort(v.begin(), v.end(),
[](int a, int b){ return a > b; });

Use cases:
• Sort by second value in pair
• Custom order problems
• Greedy strategies

[Sai jayadeep @Saijayadeep7]

SYSTEM DESIGN
Day 11 Stateless system

What it is:
A system that remembers nothing between requests.
Why it exists:
No memory makes systems simpler and easier to scale

Tiny example:
Search page:every search is treated as new
Mental note:
Stateless=no past,only present request