Скачать или смотреть How to Remove the Last x Elements from Each Row of a 2D Array in Java

Learn how to effectively remove the last `x` elements from each row of a 2D array in Java using a custom method, even with varying row lengths.
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This video is based on the question https://stackoverflow.com/q/67533915/ asked by the user 'Ciro Mertens' ( https://stackoverflow.com/u/15393275/ ) and on the answer https://stackoverflow.com/a/67535291/ provided by the user 'WJS' ( https://stackoverflow.com/u/1552534/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

In programming, handling 2D arrays (or matrices) can be a common yet challenging task, especially when dealing with rows of varying lengths. In this guide, we will tackle the problem of removing the last x elements from each row of a 2D array in Java.

Imagine you have a 2-dimensional array where each row does not necessarily contain the same number of elements. Your goal is to create a method that takes an integer input, specifying how many elements to remove from the end of each row. Let’s break down how to achieve this step by step!

Problem Overview

Consider the following example of a 2D array:

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If the user specifies to remove 2 elements from each row, the desired output would be:

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The challenge lies in the fact that some rows may be empty or null, and you also cannot use utility methods like Arrays.copyOf() for this task.

Solution Breakdown

Step 1: Method Definition

We will define a method named cutAway that takes two parameters: the original 2D array and the number of elements to cut away.

Step 2: Initialize the New Array

To handle rows of different lengths, initiate the new 2D array without specifying the column size. This allows you to dynamically create arrays based on the content of each row:

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Step 3: Loop Through the Rows

We will loop through each row of the original array to determine how many elements to keep and to handle nulls:

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Step 4: Check Conditions and Create New Row

For each row, we need to check if it’s not null and has enough elements to remove. If so, create a new array for the elements that should remain:

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Step 5: Copy Remaining Elements

Next, we copy the remaining elements from the source array to the destination array:

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Full Method Implementation

Here is the complete implementation of the cutAway method:

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Example Usage

Here is how you would use this method in practice:

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This will output:

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Conclusion

Handling 2D arrays in Java, especially with variable row lengths, can seem daunting at first, but with a structured approach, it becomes manageable. By following the steps detailed above, you can efficiently remove the last x elements from each row of a matrix, regardless of whether the rows are full, null, or empty. As you practice these concepts, you’ll improve your programming skills and confidence in dealing with arrays.

If you have any questions or comments about this method or alternative strategies, feel free to share below!