Do jagged arrays exist in C/C++?

The reason you got the error is that you must specify the bounds for at least the outer dimension; i.e.

int jagged[][3] = {{0,1},{1,2,3}};

You cannot have jagged[0] be a 2-element array of int and jagged[1] be a 3-element array of int; an N-element array is a different type from an M-element array (where N != M), and all elements of an array must be the same type.

What you can do is what the others have suggested above and create jagged as an array of pointers to int; that way each element can point to integer arrays of different sizes:

int row0[] = {0,1};
int row1[] = {1,2,3};
int *jagged[] = {row0, row1};

Even though row0 and row1 are different types (2-element vs. 3-element arrays of int), in the context of the initializer they are both implicitly converted to the same type (int *).