﻿ Java exercises: Rearrange a given array of unique elements such that every second element of the array is greater than its left and right elements - w3resource # Java Array Exercises: Rearrange a given array of unique elements such that every second element of the array is greater than its left and right elements

## Java Array: Exercise-61 with Solution

Write a Java program to rearrange a given array of unique elements such that every second element of the array is greater than its left and right elements.

Example:
Input :
nums= { 1, 2, 4, 9, 5, 3, 8, 7, 10, 12, 14 }
Output:
Array with every second element is greater than its left and right elements:
[1, 4, 2, 9, 3, 8, 5, 10, 7, 14, 12]

Sample Solution:

Java Code:

``````import java.util.Arrays;

class solution
{
private static void swap_nums(int[] nums, int i, int j) {
int t_nums = nums[i];
nums[i] = nums[j];
nums[j] = t_nums;
}

public static void rearrange_Array_nums(int[] nums)
{
for (int i = 1; i < nums.length; i += 2)
{
if (nums[i - 1] > nums[i]) {
swap_nums(nums, i - 1, i);
}

if (i + 1 < nums.length && nums[i + 1] > nums[i]) {
swap_nums(nums, i + 1, i);
}
}
}

public static void main (String[] args)
{
int[] nums= { 1, 2, 4, 9, 5, 3, 8, 7, 10, 12, 14 };
System.out.println("Original array:\n"+Arrays.toString(nums));
rearrange_Array_nums(nums);
System.out.println("\nArray with every second element is greater than its left and right elements:\n"+Arrays.toString(nums));
}
}
```
```

Sample Output:

```Original array:
[1, 2, 4, 9, 5, 3, 8, 7, 10, 12, 14]

Array with every second element is greater than its left and right elements:
[1, 4, 2, 9, 3, 8, 5, 10, 7, 14, 12]
```

Flowchart: Java Code Editor:

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## Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH