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Problem of the day

Given a sequence of numbers ‘ARR’. Your task is to return a sorted sequence of ‘ARR’ in non-descending order with help of the merge sort algorithm.

Example :

```
Merge Sort Algorithm -
Merge sort is a Divide and Conquer based Algorithm. It divides the input array into two-parts, until the size of the input array is not ‘1’. In the return part, it will merge two sorted arrays a return a whole merged sorted array.
```

```
The above illustrates shows how merge sort works.
```

```
It is compulsory to use the ‘Merge Sort’ algorithm.
```

Detailed explanation

```
The first line of input contains an integer ‘T’ denoting the number of test cases.
The next 2*'T' lines represent the ‘T’ test cases.
The first line of each test case contains an integer ‘N’ which denotes the size of ‘ARR’.
The second line of each test case contains ‘N’ space-separated elements of ‘ARR’.
```

```
For each test case, print the numbers in non-descending order
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You are not required to print the expected output; it has already been taken care of. Just implement the function.
```

```
1 <= T <= 50
1 <= N <= 10^4
-10^9 <= arr[i] <= 10^9
Time Limit : 1 sec
```

```
2
7
3 4 1 6 2 5 7
4
4 3 1 2
```

```
1 2 3 4 5 6 7
1 2 3 4
```

```
Test Case 1 :
Given ‘ARR’ : { 3, 4, 1, 6, 2, 5, 7 }
Then sorted 'ARR' in non-descending order will be : { 1, 2, 3, 4, 5, 6, 7 }. Non-descending order means every element must be greater than or equal to the previse element.
Test Case 2 :
Given ‘ARR’ : { 4, 3, 1, 2 }
Then sorted 'ARR' in non-descending order will be : { 1, 2, 3, 4 }.
```

```
2
4
5 4 6 7
3
2 1 1
```

```
4 5 6 7
1 1 2
```