Can anyone explain following code

Question

int[ ][ ] myArr = { {1, 2, 3}, {4}, {5, 6, 7} };
myArr[0][2] = 42;
int x = myArr[1][0]; // 4

Answer 1

That saves 42 to that element. At the initialization that element was set to 3.

Answer 2

Write it down as a table to understand it:
1 2 3 | a [0][0] a [0][1] a [0][2]
4 | a [1][0]
5 6 7 | a [2][0] a [2][1] a [2][2]

Answer 3

but why myArr[0][2] = 42;

Answer 4

thanks