Flatten 2D Array Problem

Implement an iterator called ‘FLATTEN_2D’ to transform a two-dimensional array ‘ARR_2D’ into a one-dimensional array ‘ARR_1D’. The iterator should support the following operations:

• NEXT: Returns the next element in the row-wise traversal of ‘ARR_2D’. The first call should return the first element from ‘ARR_2D’.
• HAS_NEXT: Returns ‘true’ if there are more elements to traverse; otherwise, return ‘false’ if the iteration is complete.

Example:

Input:

ARR_2D = [ [0, 1], [2, 3, 4], [], [5] ]

Output:

ARR_1D = [0, 1, 2, 3, 4, 5]

Explanation:

The elements of the 2D array are traversed row-wise and combined into a single 1D array.

Input Format:

The first line of input contains an integer ‘T’ indicating the number of test cases. Each test case consists of:

• An integer ‘N’ indicating the number of rows in ‘ARR_2D’.
• For each row, an integer ‘M’ indicating the number of columns followed by ‘M’ space-separated integers representing the row elements.

Output Format:

For each test case, output the elements of ‘ARR_1D’ on a separate line.

Constraints:

• 1 <= T <= 10
• 1 <= N <= 100
• 0 <= M <= 100
• -10^6 <= Value in each element of ‘ARR_2D’ <= 10^6

Note:

You are not required to print the output; your task is to implement the function for these operations.