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DATA STRUCTURES
AND ALGORITHMS

Part 1

1: Intro to programming and flowcharts
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We will also learn about
programming languages and why we use them
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This will
be our flow whenever we will solve any problem
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Bhaiya explains that a flowchart is a diagrammatic
approach of that approach known as flow chart
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He says that from where a program is starting we
have a component called terminator
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Next block is a simple rectangle, which shows a process
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He says the pseudocode as a whole is a
generic way of representing logic
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We use parallelogram to show the input/output of the
program
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If a < b print `` YES '' else print `` NO '' and it's done Simple You just have to
write in English what you are thinking and it is called pseudocode
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We have to check whether N is ODD or
EVEN , so we will make one block for this condition
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We have to print something and then increment too You have to Print and then increase the
printed number too You can see here , we printed and then increased the number by 1 But we

do n't know how to do it How we will increase again and again Let 's rub it You know that we
have to start from 1 and print till 5 So if I give you a number which starts from 1 to 5, will it
work ? You are like , yes , this is what we needed So I took a number =1 This is not an input ,
it is a process , so I wrote it inside a rectangular block
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The catch is , 1 and N are inclusive here in the
answer should be 15
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We know that we have to start with num=1 and increment it till I know N = 5 , Num
=1 , and sum =0 in the beginning
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You will get your homework after this
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Flowchart shows how to add conditions, loops, input/output, processing, processing and
start/end
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We will answer only 2 questions - What is it ? and why do we use it? You will get
your homework questions too
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Next lecture will be out tomorrow - most
probably where we will be writing our first C++ program - Namaste Duniya ( Hello world ) As
homework, you have to write pseudocodes for all the questions we have solved today
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We will see how a program runs and what each line
means in this lecture
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Coding Ninjas has supported us in providing this
amazing DSA course to you
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you need an
IDE to write, run and execute a code
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You can directly
create a C++ there and run it using Replit
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We
use these signs to output the result into standard namespace
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We are going to talk about data types and variables
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You have to mention what type of data it is and how
much memory it will take
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We have certain rules which we have to follow when we are giving names
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In memory, the first 29 bits will have 0, and the last 3 bits will be 101, so in memory
the first 29 bits will have 0 and the last 3 bits will have 101
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In c++, all the characters are mapped to
some ASCII value in memory
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If we have 4 different bytes with some binary value, how will the compiler know whether it is
a single Int value of 4 separate char values ? Compiler will come to know from data types
which we used when we declared any variable
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There are a few steps which I have to follow while storing a negative number
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With this our maximum value will be limited to 2^31 -1
instead of 2^32 -1
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4 , why ? Because you are storing your answer in
an int variable
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If you want to check
whether A is equal to B or not I can do that using this ( a==b ) relational operator = , > , < , ! =

is an assignment operator, because we are assigning 3 to a
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We have got the basic idea of operators
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Now let 's move ahead towards bitwise operators
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We will do Bitwise operators later
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We will make a
simple program , where we will ask the computer to print A if A is bigger than B , else print B
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If you are given a number
A , and you are told that print +ve if A is positive, otherwise, print not +ve
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If A is 5 , then 'if A is -2 and if a is -5, then it
will print anything
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But if I add a 'else' block here, then this block is executed
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get ( )
takes input in the form of characters
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Cin doesn't read
SPACE , TAB , ENTER and TAB
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Let 's code that
tells us which number is greater
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Entered A as 15 It printed A is positive This time I entered -1
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Correct output
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You just have to enter a
condition and the statements which you want to execute
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Here is your homework question
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We have to tell whether n is prime or not, a prime number is a number
which has only 1 and N as its factor
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% tells us
the remainder when we divide 2 numbers
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If no such number exists, then it is a prime number
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We will
do many patterns problems in the next video
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But first let 's understand this code
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J will also run from 1- N and we simply have to
print the row number
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4: Solving Pattern Questions (Part-2)
Love Babbar: We are going to solve 18 pattern questions in this video
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We also did 2 pattern questions
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Let 's try this approach
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We know that row = n
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Outside this loop , we will enter a new line and increment ' i'
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Then after printing it inside the col loop , we will keep
on incrementing it by 1
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We can't simply print a row and increment it , because then our program
will misbehave
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We have done 9 pattern questions
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Next pattern looks like this: 1st obs - row = n 2nd obs- A is mapped to 1 , B is
mapping to 2 and so on
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We got our counting correct but just had to map 1 to ' A ' so to do so , we added ' A
-1 on both sides , so to
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We just have to print ' A'+i -1 , but it will be typecasted to
integer so to avoid that
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Then
increment col , added a new line outside the col while loop and then increment row too
Simple You have to implement it by yourself
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If you are not able to do this question by yourself, then revise these first
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We know that it is written in the
reverse order
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We will get the answer the same for each row
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formula is ' A ' + row + col -2'
It was a very easy question
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After that it became
very simple
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Do this one Now let 's try out this variant
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You can see that before printing these characters , we have to print some spaces too
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These are

very easy questions if you have understood previous questions
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If you are able to do this one
without my help, then it is very good for you
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I will tell you the solution and then give you one more question to try as your
homework
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In the next one , we will see operators , bitwise
operators , For loop , and many more interesting things
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Also tell the answers in the comment section for the questions which I asked inbetween of
the video
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We have already covered the while loop , today
we will see the FOR loop
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Today we
are going to solve easy and medium level questions on Leetcode
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We have already seen this conversion in the previous lectures
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So we got our
answer as -3 Got it Bhaiya says
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We will talk about left shift and right shift operators
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For smaller numbers we will get our answer
as 2 * n But in some cases it creates negative numbers This is your left shift operator
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Bhaiya: What does post increment mean i++ It means that first use the value and then
increment it by 1 Let 's see with an example If i=4 and I write it as int a = i++ Now let 's check
what are the values of ' a ' and ' i' Post increment means , increment after using , so it means
' a will be having the old value of i which is 4 in this case and i ' is incremented after this
operation , it means i is 5 now Got ? You must see the 5 questions and you have to tell the
output in the comment section
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You can simply write this also for ( ; ; ) You should also play with these operators
because they are very easy and are asked in MCQs
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You come here only once ,
then you come to this condition
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You can use any loop from FOR loop or WHILE loop See it is giving correct output
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If it gets divided by any number, then it is not a prime number
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If we don't divide then we have to
check for other numbers because it may give 0 with them
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We are familiar with both break and continue
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We came to know that it is not a prime number
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If I redeclare B twice in the
same block , then I will get this error
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Operator precedence table increases from bottom to top and left to right
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We have to run the loop until
the N is 0 in rem =n % 10 in rem
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In this chapter, we talked about operators,
For loop, precedence, precedence and variable scope
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6: Binary & Decimal Number System

We will see how we can convert a number from one number system to the other
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So this video is
sponsored by Releval
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Bhaiya explains how algorithms help us to convert this decimal to binary in
code
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Then we will find the last
bit by doing & with 1
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Then this is the output
which we got = 0 1 0 0 1 1 0 1
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Let 's code it First
take the input of N
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After that we will get the
last digit like this After initialising and with 0 in the beginning , we will write , ans = ( digit *
pow ( 10 , i ) + ans) Ooh , it gave us 125
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We developed a logic from there that we can represent any binary number in power of 2
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Similarly we will multiply it by 2 while converting binary
numbers to decimal
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Then we will check the bit
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This is how we came to know what mistake we were making
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If you are trying to find the bit , then 123 will be represented something like
this in binary
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find the
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If it is one, we added 2 's
power to our answer , else we skipped this value
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7: LeetCode Problem Solving Session
We solved 2 leetcode problems in one of the previous videos
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We will learn some new concepts while solving these
questions
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If you want to purchase any
of their courses, then you can use the link given in the description and get 25% on all of their
courses
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We have only handled the normal case
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We know that integer has this min range and this max
range
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So we have to multiply
carefully by keeping this thing in mind that the result should not exceed the integer limit
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We know that we are given a number , we have to play with its bits
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Till now, we have seen these bits operators- AND, OR, NOT, XOR, Left shift ,
Right shift So we are going to use these operators to get our answer
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We have a variable mask which will help me in ignoring these
initial bits
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001
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We are left shifting and adding 1 to it by taking its OR with 1
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ans = ( ~n ) & mask and at the end we have to return the ans Let 's run it and see
Accepted See it is giving correct answer for all given test cases
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0000,
left shifted it with 1 and took its OR with 1 Then we repeated these steps for x times to get
our desired mask
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We will get this X
by right shifting this number again and again until we get 0 Take 5-6 examples and dry run it
over them to understand this
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We are calculating 2 's power multiple times
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This way we will keep on using the previous answer and need not to calculate
the same power again and again
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We
have used various keywords like - switch, case, default, expression, constant
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We will understand this more clearly with an
example , but for now , keep this thing in mind that you ca n't use any float or string value
here
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Once they are executed, it will execute
all other cases written below it
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It is similar to this if-else ladder ladder
which we saw in the starting
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You have to make a simple calculator today
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We took input
of a , b and operation Now we will write a switch case something like this 1st case will
perform addition, 2nd case - subtraction, 3rd case - multiplication, 4th case - divide, 5th case
of modulus
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We missed this symbol
here and we missed this one too
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A
function is a program which takes input and gives us output
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We are writing the same code again and again
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Our code is becoming bulky Our code length is increasing Let 's say you made a mistake in
the first place and then copied same code 10 times
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We have to write a return type = int then we will write the name of
the function = int power
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At last you will write return , and return your answer, and
then this answer is stored inside this 'ans' variable
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Let 's understand this function again so that it becomes clear to you
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The names of the variables in the calling function and

the Power function are different
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I will add space instead of a newline instead of newline to
make it easier to read the code
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We used to divide it
with every number from 2 to n-1
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If that is not the case, then then it's a prime number
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Is this code bulky ?
No It became easy for me to fix bugs in the code
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IS this code readable ? Yes We have divided our code into different sections
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When it 's work is over , it will
pop out of this stack
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stack , you will be able to visualise
how your function is working and calling other functions
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At last program is an easy concept when I write this
main ( ) function here
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Inshort , we have a variable 'n ' in this main function , we
passed it to the function where it got incremented and got printed as 'n+1' In Short, dummy
created a copy of the variable to use the value of 'n' When we just give the copy of a variable
to any function to use it , we call it as pass by value
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9: Introduction to Arrays in C++
Love Bubbar starts with lecture 9 and we will talk about arrays
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To take
part in this firstly you will have to register yourself for the test
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You will also have to attend the interviews and then you will get the
offers and all the process just takes 15 days and you will be hired
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The values stored in contiguous locations all things
are stored at contiguous locations means int a then we have a block in our memory which
contains some values garbage value
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We understood what an array is
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Today you learn how to initialise an array there are many ways like i want all
my array int array [ 100000 ] so I am not gon na write all the values so let us assume i have to
initialise it from 0 if we don't write 0 in this case you will get 100000 values and contains
some garbage values and no one will know the actual value something random comes
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We need only the name of the array and index
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If i start a loop 0-1 and put i
in this , will it work ? for { int i =0 ; i < n ; i + + ) { cout < < third [ i ] < < `` `` ; }
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Size will be entered by you
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We should not use a variable to define an array 's size
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I'll teach you when

you take size as a variable
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When you will come out of this loop you will
have your max value ready
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When I was in college, there was a subject called `` Intro to Programming '' in our first
semester and there we had to reverse the string
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Even if you are afraid of
solving this question , then I must say that you should not
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Reverse function start = 0 , end = n-1 and reverse function reverse
function print the array
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These are some of the questions we will do in the next lecture
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So tell me in the
comments how was today 's lecture
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If
you are finding it boring, leave it
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If you consider Amazon as a
good company then I can help you in cracking them
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The answer is 2,1,4,3,6,5
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You can find a discord server
link at the description
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Coding ninja is the largest coding education platform where you can see interesting
courses and if you're interested in paid courses and want to develop yourself learn machine
learning , android , core subjects , DSA with any language like java and python
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We
have an array here So we will deal with both of them
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Assume that 6 of them are greater or let "s say 8 are greater
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odd [ 5 ] = I have written here
11,33,9,76,43 in this way
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Therefore it was 8
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Let 's run it 2 times
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6,7 and then 0,1 It 's going perfect
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Then
here it is odd and its size would be 5 and then run it
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i+=2 inside the for loop which
means the same as i=i+2
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We have to swap
the value of 0th and 1st index
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The link to all the questions will be given in the
description itself
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And now I have to update the 0th index which is an array of 0
and inside it should be 2
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What do they mean ? They meant to say that in your array the M
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But one single number appears only once and others appear
twice
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In
this way we have printed 1 why because here 2 is present two times
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In this case 2 and 7 appear twice, 4 is left
so the desired answer is 4 next
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But what even is the point of storing it will remain the same
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We had to XOR 2, 3,1,6,3,6 and 2 to solve
our first question
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The question says Given a number of integers array you have given an array of integers in
that array
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Next -3
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let me just solve it for you
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This question's unique concept is that
you have to solve it
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Next question is Find duplicates in an array
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It is
easy while solving but it is very famous for finding duplicates
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X ,
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In that way these numbers
will be present
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It will cancel out if I try to apply for XOR
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That is what we require so your game is complete so
i have to think something to cancel out this

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