About 2D array

Question

I used round bracket instead of parenthesis to check wheather it affects the code or not. It did and I'm unable to understand the difference. With parenthesis ,it give 1 as output while using round bracket ans is 3.Can someone explain why ?
https://code.sololearn.com/cbdf27Vp8llV/?ref=app

Answer 1

Iterator
int a = (foo(), bar() + 13, 0);
a == 0;

Answer 2

You made an expressions with operation ",". The result of the expressions is the last value in round brackets.
You initialized only first row of the array.

Answer 3

Tind you right. Operators' priority is my weakness.