**Objective: **Given k sorted array, write an algorithm to merge Them into One sorted array.

**Example :**

int[][] A =newint[5][]; A[0] =newint[] { 1, 5, 8, 9 }; A[1] =newint[] { 2, 3, 7, 10 }; A[2] =newint[] { 4, 6, 11, 15 }; A[3] =newint[] { 9, 14, 16, 19 }; A[4] =newint[] { 2, 4, 6, 9 }; Output: [1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 9, 9, 9, 10, 11, 14, 15, 16, 19]

**Naive Solution: O(nkLognk)**

- Create an result[] of size n*k.
- Copy all the elements from k arrays into result array. This will take O(nk).
- Sort the result[] using Merge Sort. This will take O(nkLognk) time.

**Better Approach: O(nkLogk)**

- Create an
**result[]**of size n*k. - Create Min-Heap of type HeapNode.(
**HeapNode-**Every Node will store the data and the list no from which it belongs). - Now take one element from each of the K list and create HeapNode object and insert into min-Heap.
- Extract the minimum Node from the min-Heap, insert the data into result array.
- The extracted node will also contain the list to which it belongs, insert the next element from that list into min-Heap.
- If any point of time any list gets over, insert +∞ into min-Heap.
- Keep repeating until all the K list gets over.

See the animation below for better understanding.

**Complete Code:**

https://gist.github.com/thmain/388c17200e10dab61a5a

**Output**:

[1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 9, 9, 9, 10, 11, 14, 15, 16, 19]