Why my diagonal difference is not working properly?

Question

https://code.sololearn.com/cudkTc5L9u41/?ref=app

Answer 1

Abhay mishra you would actually want the sum of i+j to equal arr[0].size or in your case r.
In otherwords the sum of the indexes should equal the row or column length.
0 1 2
0 X
1 X
2 X

0 1 2 3
0 X
1 X
2 X
3 X

Answer 2

Abhay mishra I am working on the compilation errors.
Some of them are just from deprecated function calls.

They should be able to be replaced with the suggested functions.

As a question. What should the input for this code look like?
I believe that I have it, however it would help to ensure that I am analyzing this correctly.