Merge K sorted arrays!

You are given K sorted integer arrays in a form of 2D integer matrix A of size K X N.

You need to merge them into a single array and return it.

1 <= K, N <= 10³

0 <= A[i][j] <= 10⁸

A[i][j] <= A[i][j+1]

First and only argument is an 2D integer matrix A.

Return a integer array denoting the merged array you get after merging all the arrays in A.

Input 1:

 A = [  [1, 2, 3]
        [2, 4, 6]
        [0, 9, 10]
     ]

Output 1:

 [0, 1, 2, 2, 3, 4, 6, 9, 10]

Explanation 1:

 You need to merge [1, 2, 3] , [2, 4, 6] and [0, 9, 10]  into a single array
 so the merged array will look like [0, 1, 2, 2, 3, 4, 6, 9, 10]