Data Structures and Algorithms in 15 Minutes
Summary
TLDRThis video script offers a humorous and insightful journey into the world of data structures and algorithms, essential for computer science enthusiasts. It humorously addresses the challenges and rewards of mastering these concepts, which are crucial for problem-solving efficiency and highly valued by tech companies. The script covers various data structures like arrays, linked lists, binary trees, and heaps, and algorithms including sorting, searching, and graph theory. It also touches on the importance of understanding time and space complexity, and provides learning resources for further study, emphasizing the value of a broad understanding before delving into deeper details.
Takeaways
- 😎 Being proficient in data structures and algorithms is highly valued in the tech industry, often associated with high intellect and attractive job offers.
- 🚀 The journey to mastering algorithms and data structures is challenging and can be filled with frustration and feelings of imposter syndrome.
- 💡 The motivation to learn should stem from a genuine interest in problem-solving efficiency rather than just for job prospects.
- 📈 Understanding algorithm efficiency involves recognizing the relationship between input size and the number of operations required, often described using Big O notation.
- 🔍 Different algorithms have distinct time complexities, such as constant, linear, quadratic, logarithmic, exponential, and factorial, which greatly affect performance with varying input sizes.
- 🌲 Data structures like arrays, linked lists, and binary trees, each with their own properties and use cases, are fundamental to computer science.
- 🔄 Sorting algorithms, including selection sort and merge sort, have different time complexities, with merge sort being notably efficient at O(n log n).
- 🌐 Graphs, with their vertices and edges, are used to model complex relationships and can be manipulated to find shortest paths or perform topological sorts.
- 🔑 Hash maps offer nearly constant time data retrieval and are built on arrays with a hash function to map keys to indices, making them extremely powerful for data storage and access.
- 🎓 Learning data structures and algorithms is more effective when approached with a general understanding first, followed by deeper dives into specific topics.
Q & A
Why is being proficient in data structures and algorithms considered prestigious in the computer science field?
-Proficiency in data structures and algorithms is considered prestigious because it signifies a deep understanding of efficient problem-solving in computer science. It often leads to high-paying job offers from prestigious companies and is associated with high social market value in online tech communities.
What is the significance of Big O notation in computer science?
-Big O notation is used to describe the time complexity of an algorithm, which is the relationship between the growth of input size and the growth of the number of operations required. It helps in comparing the efficiency of different algorithms and is crucial for optimizing performance.
How does the efficiency of an algorithm impact the performance of a program?
-The efficiency of an algorithm directly impacts the performance of a program by determining how the execution time and resources required scale with the input size. Inefficient algorithms can lead to excessive resource usage and slow execution times, especially with large inputs.
What is the difference between a constant time and a linear time algorithm?
-A constant time algorithm has a fixed number of operations, regardless of the input size, often represented as O(1). In contrast, a linear time algorithm's operation count grows proportionally with the input size, represented as O(n), where 'n' is the input size.
Why is it important to understand logarithms when studying algorithms?
-Logarithms are important in algorithm studies because they often represent the efficiency of algorithms that involve dividing the problem size by half with each step, such as binary search. Understanding logarithms helps in grasping the concept of logarithmic time complexity, which is significant for algorithms like binary search and merge sort.
What is a binary search and how does it work?
-A binary search is an efficient algorithm for finding an item from a sorted list of items. It works by repeatedly dividing the search interval in half. If the value of the search key is less than the item in the middle of the interval, narrow the interval to the lower half. Otherwise, narrow it to the upper half. Repeatedly check until the value is found or the interval is empty.
Why is sorting important in computer science, and what is the best time complexity we can achieve for sorting?
-Sorting is important in computer science because it is a fundamental operation that prepares data for efficient searching, processing, and analysis. The best time complexity we can achieve for sorting an arbitrary collection is O(n log n), which is the time complexity of algorithms like merge sort.
What is the primary difference between an array and a linked list?
-The primary difference is that an array is a fixed-size, contiguous block of memory where elements can be accessed directly by index, while a linked list is a flexible-size data structure composed of nodes that contain data and a reference to the next node in the sequence. Linked lists allow for efficient insertion and deletion but do not support direct access by index.
How does a binary search tree differ from a binary tree, and what are its properties?
-A binary search tree is a specific type of binary tree with the property that the value of each node is greater than or equal to any value stored in the left subtree and less than any value in the right subtree. This ordering property makes binary search trees efficient for searching, insertion, and deletion operations.
What is a heap, and how does it differ from a binary search tree?
-A heap is a specialized tree-based data structure that satisfies the heap property: either the parent node is always greater than or equal to (in a max heap) or less than or equal to (in a min heap) any of its children. Unlike binary search trees, heaps are not necessarily sorted, and the primary focus is on the priority of the root element, which is the highest or lowest value in the heap.
What are the two main ways to traverse a tree, and how do they differ?
-The two main ways to traverse a tree are depth-first search (DFS) and breadth-first search (BFS). DFS explores as far as possible along each branch before backtracking, while BFS visits all the nodes at the present depth level before moving on to nodes at the next depth level.
Outlines
🧠 The Journey to Algorithm Mastery
The paragraph introduces the significance of mastering data structures and algorithms in computer science, likening it to a status symbol that can lead to high-paying job offers and social recognition. It candidly discusses the challenges faced by learners, such as frustration and imposter syndrome. The speaker, having overcome these obstacles, shares a personal anecdote about receiving job offers, humorously suggesting their qualifications are now so high they could 'cure cancer.' The video aims to serve as a guide for those struggling with programming concepts, emphasizing the importance of intrinsic motivation over extrinsic goals like employment at prestigious companies. It delves into the fundamentals of algorithm efficiency, explaining time complexity through examples and introducing Big O notation as a tool for expressing this complexity. The paragraph concludes with a discussion on different types of time complexities, such as constant, linear, quadratic, logarithmic, exponential, and factorial, using relatable examples to illustrate these concepts.
🌲 Exploring Data Structures: Arrays, Linked Lists, and Trees
This segment delves into various data structures, starting with arrays and their limitations, such as fixed size. It contrasts arrays with linked lists, which offer dynamic sizing through nodes that contain data and a reference to the next node. The narrative humorously compares traversing a linked list to following a chain of YouTube comments leading to a potential virus. It also touches on doubly linked lists and the efficiency of adding, inserting, and deleting nodes. The paragraph then transitions into binary trees, explaining their structure and the concept of binary search trees, which maintain a sorted order through rules about child node values. It discusses the average and worst-case time complexities for operations on these trees and introduces self-balancing binary search trees like red-black trees. The speaker also briefly mentions heaps, another tree-based data structure used for priority queues, and different traversal methods like depth-first search (DFS) and breadth-first search (BFS), providing examples of how these methods can be implemented.
🔍 Graphs and Their Applications
The focus of this paragraph is on graphs, which are collections of vertices and edges that can be used to model complex relationships and networks. It starts by differentiating between directed and undirected graphs and explains how edges can be represented using adjacency lists or matrices. The speaker then explores various applications of graphs, such as calculating degrees of separation in social networks, finding the shortest path in map systems like Google Maps, and performing topological sorting for course scheduling. Each application is tied to a specific algorithm: breadth-first search for degrees of separation, Dijkstra's algorithm for weighted shortest paths, and a queue-based approach for topological sorting. The paragraph highlights the versatility and importance of graphs in solving real-world problems and emphasizes the practicality of these algorithms.
🔑 The Power of Hash Maps
The final paragraph emphasizes the utility of hash maps, a data structure that provides efficient data retrieval through key-value pairs. It describes hash maps as the 'holy grail' of data structures due to their ability to offer constant time complexity for operations like retrieval, insertion, and deletion. The speaker explains the concept of a hash function, which converts keys into hash codes that are used as indices in an underlying array. Collisions, where different keys produce the same hash code, are discussed, and the use of linked lists to resolve these is introduced. The paragraph concludes with a recommendation for learning resources, including a paid course with a community aspect and free college lectures, suggesting that both paid and free options can lead to mastery of data structures and algorithms.
Mindmap
Keywords
💡Data Structures
💡Algorithms
💡Big O Notation
💡Time Complexity
💡Space Complexity
💡Binary Search
💡Merge Sort
💡Linked List
💡Graphs
💡Hash Maps
Highlights
Being proficient in data structures and algorithms is highly valued in computer science, often equating to high social market value and prestigious job offers.
The journey to mastering algorithms is challenging and can be filled with frustration and imposter syndrome.
Having a genuine interest in learning data structures and algorithms, rather than just for job prospects, is crucial for success.
Understanding how to rank an algorithm's efficiency is fundamental, with big O notation used to describe time complexity.
Different algorithms have varying time complexities, such as linear, constant, and logarithmic, which affect how they scale with input size.
Big O notation is also used for space complexity, indicating how much memory an algorithm uses relative to input size.
Logarithms are the inverse of exponential functions and play a key role in algorithms like binary search.
Binary search is an efficient algorithm for finding items in a sorted list by repeatedly dividing the search interval in half.
Sorting algorithms like selection sort and merge sort have different time complexities, with merge sort being more efficient at O(n log n).
Arrays and linked lists are basic data structures with different properties, such as fixed size versus dynamic size.
Linked lists allow for efficient insertion and deletion of nodes but do not support constant time access by index.
Binary trees, such as binary search trees, enable efficient searching, insertion, and deletion with a time complexity related to the tree's height.
Self-balancing binary search trees like red-black trees ensure a logarithmic height, maintaining efficient operations.
Heaps are tree-like data structures that store elements according to priority, with the highest priority element always at the root.
Depth-first and breadth-first searches are methods for traversing trees and graphs, with each having its own order and use cases.
Graphs are used to model complex relationships and can be used to find shortest paths, such as in social networks or mapping systems.
Hash maps provide constant time retrieval of data and are built on arrays with a hash function to compute indices for keys.
Collisions in hash maps can be resolved using linked lists or other methods to maintain efficient data retrieval.
Data structures and algorithms are essential for solving problems efficiently and should be learned for their problem-solving benefits, not just for job prospects.
Transcripts
being good at data structures and
algorithms is a computer science
equivalent of having
i mean everyone assumes you're a genius
you get high paying offers from
prestigious companies
and you even have a high social market
value on internet forums but the journey
from lead cell to algo chat is not an
easy one
it's filled with frustration and
imposter syndrome i know i've been there
but now i have offers from feng which
basically qualifies me to cure cancer
so to give back and help even the most
confusing programmers
consider this video my cure since this
industry is cancer
[Music]
the most important part of learning
something new is that you actually want
to learn it
this is why i failed out of spanish one
so before we start
ask yourself why do you want to learn
this don't do it to get a job at google
do it because learning this changes the
way you think data structures and
algorithms
is about solving problems efficiently a
bad programmer solves the problem
inefficiently and a
really bad programmer doesn't even know
why their solution is inefficient so
let's start with that
how do we rank an algorithm's efficiency
[Music]
say we wrote a function that goes
through every number in a list and adds
it to a total sum variable if you
consider
adding to be one operation then running
this function on a list with 10 numbers
costs 10 operations running it on a list
with 20 numbers costs 20 operations
say we wrote another function that just
returns the first number in a list then
no matter how large the list is this
function will never cost more than one
operation
clearly these two algorithms have a
different time complexity or
relationship between growth of input
size and growth of operations we
communicate these time complexities
using big
o notation referring to input size as n
common complexities are
constant linear quadratic
logarithmic n log n exponential
and factorial our first algorithm runs
in o of n
meaning its operations grow in a linear
relationship with the input size which
in this case is the amount of numbers in
the list our second algorithm
is not dependent on the input size at
all so it runs in constant time let's
take a look at how many operations a
program will have to execute in a
function with an input size of 5
versus 50. it might not matter when the
input is small but this gap gets very
dramatic as the input size increases if
n were 10
000 a function that runs in log of n
would only take 14 operations while the
function that runs in n factorial
would set your computer on fire for big
o notation we drop constants so
o of 10 times n and o of n over 10 are
both equivalent to o of n because the
graph is still linear and bagel notation
is also used for space complexity which
works the same way for how much space an
algorithm uses as n grows
unless you sit in your room doing
algorithms all day there's a good chance
you forgot what logarithms are
logarithms are the inverse to
exponential functions let's say i wanted
to find a word in a dictionary
one method is to check every word one by
one this is o
n but nobody does that so how are humans
able to find
any word in a dictionary with a hundred
thousand words in seconds we do
something more along method two
cut the search window in half each time
by checking the middle element
if we passed our word search on the left
half otherwise search on the right half
and then we repeat this until we find
our word
if our input n doubled in size that
would only grow our operations by one
in computer science this is the binary
search but for the binary search to work
the collection has to be sorted which
opens up a huge field of computer
science
sorting algorithms a very basic sort is
a selection sort you have one pointer at
the start of the list and another
pointer that is linear scan to find the
next minimum element
then you swap those elements and
increment the pointer since you're doing
a linear scan for every element in the
collection
this runs in all of n squared a more
efficient algorithm is the merge sort a
merged source splits a collection in
half into sub-collections until those
sub-collections can be sorted in
constant time and then it works its way
back up by merging sorted subcollections
until the entire collection is sorted
since it's splitting in half there will
be log n splits and thereby
log n merges it is o then to merge two
sorted collections into one sorted
collection
since we're doing that log n times the
time complexity is of
n times log n no algorithm can sort an
arbitrary collection in a better time
complexity than that so we consider
n log n to be the cost of sorting
perhaps the most fundamental data
structure is an array an array is an
indexable contiguous chunk of memory
arrays are fixed size you can't insert a
ninth element into an array meant for
eight elements a list data structure
with a flexible size is a linked list
the idea is to package your data into
nodes that hold one
your data and two a point that points to
the next node
traversing a linked list reminds me of
those youtube direction chains
like you see a comment that says read my
profile picture
and their profile picture says click on
my profile which brings you to their
header which says
read my bio so you go to their bio and
it says click the link below and you
click it and then it installs a virus
onto your browser
if a note's next pointer points to null
it's the end of the list you can add a
new node to the list in constant time by
just setting that pointer to the new
node
by doing additional tom [ __ ] with
pointers we can also insert and delete
nodes in constant time
sometimes nodes also contain a pointer
to the previous node in a variation
called the doubly linked list but a
major downside of linked list is that
you can't
access elements in constant time via
index like an array in practice both
programming languages have dynamically
sized arrays or lists which work by
creating arrays with a fixed size
if the array is full capacity and you
try to add a new element
the programming language automatically
creates a new array with double the
capacity
copies the current elements over and
sets your pointer to that new array
since this happens so infrequently we
generally consider appending to a list
to be a constant time operation
link lists aren't the only data
structure that include nodes referring
to other nodes what if instead of
pointing to a next node nodes pointed to
a left and a right child node this is
called a binary tree
these child notes can also be called
subtrees since trees are recursive in
nature
a node with no children is called a leaf
node while a node with seven children is
my
father-in-law a common type of tree is
the binary search tree which follows
these rules
basically a node's left child must have
a smaller value while a node's right
child must have a greater or equal value
let's say you're looking for element x
you start at the root and if the number
is smaller than the root you go to the
left tree if it's larger you go to the
right and you keep repeating this until
you arrive at your number
in the worst case you have to traverse
the height of the tree so the time
complexity to search
insert and delete elements is of h where
h is the height
this is efficient because on average the
height will be log n
but what if you inserted every element
of a sorted array into an empty binary
search tree
well that's a linked list meaning the
height would be
n but we can guarantee log n time
complexities using a self-balancing
binary search tree such as red black
trees which maintain
additional properties to guarantee that
the height of the tree is o of log n
binary search trees are kind of
considered to be a workhorse
distribution that can solve most
problems with decent efficiency but i
found situations where binary search
trees
really shine are when you're asked a
question about binary search trees
another type of tree is a heap the
primary difference between this and the
binary search tree is
actually use this one it's also
sometimes called a priority queue
because at the root of it is always the
highest priority element
and min heap will have the min element
and the max heap will have the max
element at the root but don't get me
wrong the rest of the heap is unsorted
it is an absolute wasteland down there
searching in the rest of the heap
may as well be an unsorted array we only
care about what's at the top
just like capitalism to insert a new
element into a heap
first we find the next available spot to
add a leaf node then we compare it with
his parents and if it's a higher
priority it swaps and bubbles his way up
we're doing at most
log n comparisons you can build a heap
from a random collection by inserting n
times which cost
o of n log n but there's also a way to
build a heap in o of end time
i'd suggest reading this wikipedia page
because it's super interesting stuff and
lastly
since the heap is nearly complete
although we can visualize it as a tree
we could actually use these properties
to represent it with an
array one way to traverse a tree is a
depth first search
which is like going deep fully exploring
one path and then moving on to the next
one way to visit this tree in a depth
first order could be to start at 10
go to 13 go to 4 then 6 then 12
then 8 and then 1 whereas another option
is a breadth first search where we view
it more
level by level a way to print this same
tree in a bfs manner could be
10 13 12 4 6
8 1. when it comes to implementation
depth first search can use a stack a
stack is a list-based data structure
where the only two operations
are add to the end and pop from the end
this makes a stack
lifo last in first out dfs are often
done using recursion
which indirectly uses a stack the
recursive stack so if your recursion
exceeds a certain amount of depth then
you get a stack overflow let's look at a
way to print this tree in a dfs matter
using a stack so first initialize the
stack and add the root
then while there are still elements in
the stack pop from the stack print that
element and then add its children to the
stack on the contrary a breadth first
search uses a queue
a queue is fifo first in first out so
instead of popping from the end of the
list
you pop from the beginning doing the
same algorithm as before but
using a q instead of a stack the tree
will now print in a bfs
order all trees are graphs but not all
graphs are trees a graph is a collection
of vertices which are like points
and edges which are like connections
from one vertex to another vertex a
graph can be directed meaning edges can
only go one way
so this edge means you can only go from
a to b or undirected meaning you can
also go from b to a
two common ways to model edges are
adjacency lists and adjacency matrices
graphs are my favorite part of
destruction algorithms so i'd like to
show how cool they are with three
example scenarios on where you can use
them
so it recently dawned on me that i know
kanye west
and by that i mean i know joma tech but
joma tech knows jarvis johnson who knows
mkbhd who knows elon musk
who knows kanye west which is five
degrees of separation between me and
kanye west i wanted to find something
shorter
well turns out i know bretman rock who
knows rihanna who knows kanye three
degrees of separation
which also means that anyone who knows
me is at most
four degrees of separation away from
kanye if we wanted to make a program
that computes the smallest degrees of
separation between two people
a graph would be the perfect choice you
model people as vertices and you model
relationships as edges the shortest path
between the source node
me and the target node kanye can be
found with a breath first search
since we're moving out level by level we
can guarantee that the first time
reaching the kanye node will also be the
shortest path
the problem with implementing this
algorithm the way i just described is
that
nobody has a concrete list of all the
people they know nor would that be
publicly accessible by me but a possible
variation could be in a social network
like facebook where we can use the
friend list as edges
we would then be able to run this
algorithm and find the smallest degrees
of separation between
any two users in that social network
imagine a map system like google maps
that wants to find the shortest path
between two locations
this is different than the last example
because although they both deal with
shortest paths the degrees of
separations did not have
weighted edges where a map system does
for example if we're computing the
shortest path between two vertices and
there's a direct edge between them
weighing 20 versus a path of two edges
weighing eight
each a breath first search would give us
the shortest path in terms of the
vertices away but not the smallest
weight one algorithm that computes the
shortest path in a graph with positive
weighted edges is dijkstra's algorithm
using the heap data structure in the
original version of this video
i explained dijkstra's and my video shot
up 6 minutes so instead just research it
for yourself if you're interested
but graphs aren't just good for path
finding imagine a course schedule in
school with classes
and prerequisites for each class and say
you wanted to find the order in which
you can take all your classes while
still fulfilling your prerequisites well
model the classes as vertices and
prerequisites as edges count how many
incoming edge each vertex has add
vertices with zero incoming edges to a
queue then pop and print the element
from the queue and decrement the
incoming edges of all its children
if a child now has zero incoming edges
add it to the cube and repeat while
there are still elements in the queue
this algorithm is known as a topological
sort
[Music]
hash maps are sort of the holy grail of
data structures with basically constant
time retrieval of data
the saying goes that if you don't know
what you're doing just try throwing
hashtags at the question
as an example one time i was in a coding
interview and froze so
i just told the interviewer hmm i think
the solution to use a hash map
unfortunately the question was what are
your biggest weaknesses
so the better answer was hang up the
phone to show that i have none a hashmap
is a data structure built on top of an
array optimized to store
key value pairs what makes it so
powerful is you can retrieve delete and
store data
in on average constant time here we have
a map where keys are strings
representing people's names and values
are their corresponding ages
we can directly access trend black's age
like this it's almost as if strings can
be used as indices
but how is that even possible because of
this little thing called a hash function
a hash function will take a key and
return a hash code if we take that
number modulus the length of its
underlying array we can use that as an
index to store its value but the hash
function has to compute the same hash
code if
given the same key so hash of trend
black should always return the same hash
code or else we lose the index but what
if hash of trend black and hash of ziz
both end with the same index well this
is called collision
one way to deal with this is to store
our value in a linked list
so when we go to stores is and see that
index three already has a value we have
that value
point to the new value this is why a
hash map is not strictly of one because
if you write some
god awful hash function then it won't be
balanced and we will have to do a lot of
linkless traversing good hash functions
evenly spread out hash codes
in practice modern languages use very
good hash functions so you don't have to
write your own
an example of a hashmap is the
dictionary in python or the object in
javascript and remember
constant lookup of data is very
overpowered so try to use it when you
can
[Music]
and that's pretty much all you need to
know for data structures and algorithms
a six month college course taught in 13
minutes now of course you didn't learn
anything in great detail but trust me it
is a lot easier to learn something in
great detail if you already learned the
big picture first
this is why college sucks at teaching it
dives very deep into one topic and then
moves on to the next
it's like a depth first search i believe
the better way of learning is to get a
general understanding and then build on
it
like a breath first search so if you
want to keep going what are my
recommendations to build on your
knowledge well the first one
is jomo class you know those really nice
animations in this video like this one
yeah i got them from joma class if you
don't care about getting extremely
theoretical and just want simple
to the point everything you need to know
and nothing you don't type lessons then
jomo class makes this difficult topic
very accessible but i will admit that i
roasted the
[ __ ] out of jomah a while back because
he was pushing some
actual snake oil well unlike some people
he took my criticism very well and to
vindicate his name
he made something that is actually
valuable and i will defend that
he put much more effort into these
explanations dropped the price from a
thousand dollars to eight dollars a
month and most importantly he dropped
the
dead weight if you're a complete
beginner it also comes with a course on
how to code in python and of course on
sql if you're a bit more advanced but i
gotta say the best part is the community
aspect
each lesson has a whole community behind
it where people ask questions
discuss topics and just learn together
well i like the course so much that i
actually called joma
and i was like yo what the [ __ ] dude
this is actually good i'm gonna start
recommending this to people
and he was so excited to hear that i
liked it that he was actually willing to
offer my audience a discount
so if you go to trend.jomoclass.com
then you'll get 15 off but even though
paying for stuff increases the chance
that you'll actually complete it you
don't
have to spend money not everyone has
eight dollars a month to drop and i want
to assure you that you can still learn
everything for free
so it might take a bit more
self-discipline but you can do it so
don't listen to anyone who says you
have to pay so if you do want to go down
the free route i'd recommend these
college lectures
they're literally taught by mit
professors and posted for free online
they're pretty theoretical but very
comprehensive and it's perfect if you
like that old-school
chalkboard setting so yeah good luck
guys and go get that guck 3000
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