Pointers and arrays

#1

int **arr = new int *[100];
int *arr = new int [100];

i am confused with these two lines.what is the exact difference between them.Please explain each and every part of the line…this is so confusing.

#2

Hey @kani001
So new keyword allocates memory and return address
new int creates integer dynamically
Similarly
new int[10]
Creates 10 integers dynamically which are contiguous(one after another)
Similarly
new int*[10] creates 10 pointers f integer type contiguosly

Incase u dont know pointer is a variable which holds address

Now talking about

Here it creates 100 integers contiguosly and save its starting address in arr pointer

Similarly

Here it creates 100 integer pointers contiguosuly and save its startinng address in arr pointer

Consider LHS as int* *arr that is pointer to hold address of int* type

#3

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#4

so basically in first case we create 1d array and 2nd case we create 2d array right?

#5

Hey @kani001

In this we are creating a 1-D array of integers which will have integers value like 2,3,4,5,
Whereas

In this we are creating a 1-D array of int pointers, which will point to these variables ( like 2,3,4,5,)
Still have any issue, can ask me :slight_smile:

#6

in 2nd case though we create 1d array of pointers when we again point it to a linear array,then this statement (int *arr=new int[100]) should create 2d array right?)

#7

No, it would only create a 1d array of pointers

#8

image
image1045×615 110 KB

Here 2000 2010 2050 are array of pointers of int * * arr = new int [n]
And 10 20 30 are array of integers I.e., int * arr = new int[n]

#9

in 2nd case though we create 1d array of pointers when we again point it to a linear array,then this statement (int *arr=new int[100]) should create 2d array right?)

#10

in 2nd case though we create 1d array of pointers when we again point it to a linear array,then this statement (int * *arr=new int * [100]) should create 2d array right?)

#11

Yes, if each pointer will be pointing first element of each row, then it will creat a 2d array (int * * arr = new int [n] )

#12

This is what I want to say if you have any confusion left in it.

image
image1125×834 83.9 KB

Here m is the size of pointer array
And n is the size of integer array