Zig - Zag Array

Posted: 3 Jun, 2021
Difficulty: Easy

PROBLEM STATEMENT

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You are given an array of distinct elements, and you have to rearrange the array elements in a zig-zag fashion. In other words, for every odd position ‘i’ in the array 'ARR,' 'ARR'[i] should be greater than 'ARR'[i-1] and 'ARR'[i] should be greater than 'ARR'[i+1].

For example:

Given ‘N’ = 4, 
'ARR' = { 4, 3, 2, 1} 
Then a possible array is 3, 4, 1, 2.
Note:
You are supposed to return the array, which is in a zig-zag fashion.

Since there can be multiple answers for a particular array, any of the possible solutions are accepted.

It can be proved. A zig-zag array is always possible for a given array.
Input format:
The first line of input contains an integer ‘T’ denoting the number of test cases.

The first line of each test case contains a single integer, ‘N,’ where ‘N’ is the number of elements of the array.

The second line of each test case contains ‘N’ space-separated integers, denoting the array elements.
Output Format :
For each test case, You are supposed to return a zig-zag array for the given array. The runner function will print a single line containing a single integer which denotes whether the returned array is in zig-zag fashion or not.
Note:
You are not required to print the expected output; it has already been taken care of. Just implement the function.
Constraints:
1 <= ‘T’ <= 10
1 <= ‘N’ <= 5*10^3
0 <= 'ARR'[i] <= 10 ^ 6

Time Limit: 1sec.
Approach 1

The idea is to sort the array and swap the pair of elements starting from index 1 (0-based Indexing). 


The steps are as follows: 

  • Sort the array in ascending order.
  • Loop ‘i’ = 0, from index 1 to ‘N’ and at each iteration increase ‘i’ by 2.
    • Swap elements at positions ‘i’ and ‘i + 1’.
  • We will return the array ‘arr’ as the final answer.
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