Java Sorting Arrays: How to Get Sorted Indices Based on Another Array

Learn how to effectively sort an integer array based on the values of another array in Java, and retrieve the sorted indices with clear code examples.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Java sort int[] base on another int[]

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Java Sorting Arrays: How to Get Sorted Indices Based on Another Array

Sorting arrays is a common task in programming, especially in Java. However, there are times when you need to sort one array based on the values of another array. This can become tricky, especially if you're trying to keep track of the original indices of the elements. In this guide, we'll explore a solution to this problem with a practical code example.

The Problem

Imagine you have an integer array called xCoordinates with elements representing coordinates, and you want to sort this array and output the indices of the sorted elements.

For example:

Sample Input: [20, 10, 30, 40, 50]

Expected Output: [1, 0, 2, 3, 4]

In this case, the indices represent the positions of the original elements in the sorted order.

The Initial Attempt

Here is a code snippet that someone might attempt to use to solve this problem:

[[See Video to Reveal this Text or Code Snippet]]

However, this code results in an error: "no suitable method found for sort(int[],(a,b)- arr[a] - arr[b])".

The Solution

Updated Code Solution

Here's a step-by-step breakdown of how to implement the solution:

Create an Integer Array:
Instead of using an int[], we will use Integer[] which allows us to leverage comparators for sorting.

Populate the Array:
Fill this Integer[] with the indices of the original array.

Sort with a Comparator:

Convert Back to int Array:
Finally, convert Integer[] back to int[] if needed.

Here’s the complete code:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code:

Integer Array Initialization: This creates an array that will store the indices of the original arr.

Filling Indices: The loop fills the sortedIndex array with indices from 0 to n-1.

Mapping back to int: The last line converts Integer[] back to int[] using streams.

Conclusion

By following the code snippets and explanations above, you can handle similar tasks in your own Java projects with confidence!

Remember, understanding how to manipulate and sort arrays is a crucial skill in programming that will enhance your coding abilities. Happy coding!