I m nt able to understand this code can anyone help me

Question

Major doubt is why len =60 why???
https://code.sololearn.com/c82KM7rLeVSo/?ref=app

Answer 1

bluesea i know how it came 60, i wanted to know why we want len=60 and whole program explaination
Thanx for the response

Answer 2

Your code contains error. You can allocate less memory than you use:
you store pointers to row, but size calculate as for indexes of rows in line#6
instead of
len=sizeof(int)*r+sizeof(int)*r*c
sholud be
len=sizeof(int*)*r+sizeof(int)*r*c

len can be 60 or 72 depending on platform, but in your code it is always 60 (assuming that sizeof(int) = 4)

c is num of cols
r is num of rows

arr is used to store matrix. it consists of 2 parts.
part#1 is array of pointers to each row of the matrix. its size = sizeof(int*)*r.
part#2 is matrix itself. its size = sizeof(int)*r*c
len is the total size = size of part#1 + size of part#2 = sizeof(int*)*r+sizeof(int)*r*c

r = 3, c = 4

matrix contains 3*4=12 cells.
size of each cell = sizeof(int) = 4
matrix size = 12 * 4 = 48 - it is size of part#2

space for storing 3 pointers to each row = sizeof(int*) * 3 = 12 (for 32bit platform or 24 for 64 bit machine) - it is size of part#1

len = 60 or 72 depending on platfrom.

1st loop is used to setup row pointers (part#1)
2nd loop is used to initialize a matrix to sequence of numbers
3rd loop prints matrix

Answer 3

andriy kan--> thank u so much, your explanation is awesome 🙌🙌nice one

Answer 4

@Manito,
You are welcome

Answer 5

See this it may help you to understand.

https://code.sololearn.com/cp80iLJaiNhx/?ref=app