Optimizing Array Element Removal in C with realloc

Описание: Learn how to efficiently delete the last element of a dynamic array in C using `realloc` instead of manual copying and reallocation.
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This video is based on the question https://stackoverflow.com/q/79490811/ asked by the user 'Safarov Arthur' ( https://stackoverflow.com/u/29920923/ ) and on the answer https://stackoverflow.com/a/79490821/ provided by the user 'dbush' ( https://stackoverflow.com/u/1687119/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When working with dynamic arrays in C, removing the last element often involves resizing the array. A common approach manually copies the existing elements to a new, smaller array — but this can be inefficient.

This post discusses more optimized ways to delete the last element of a dynamically allocated array.

The Common Approach: Manual Copying

A typical method is to:

Allocate a new smaller array

Copy the all but last elements from the original array

Free the original array

Replace the original pointer with the new array

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While this works, it involves unnecessary copying and extra memory allocations.

The Optimized Solution: Using realloc

The C standard library provides realloc, which adjusts the size of an allocated memory block:

It tries to resize the existing block without moving it

If needed, it moves the block and copies data internally

Using realloc directly avoids manual copying and extra malloc/free calls:

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Benefits of using realloc

Simplifies code

Potentially better performance

Handles memory resizing internally

Note: Always check the return value of realloc.

Summary

For deleting the last element of a dynamically allocated array in C:

Avoid manual allocation and copying whenever possible

Use realloc to resize the array efficiently

Ensure correct error handling for realloc failures

This approach makes your code cleaner and improves performance with fewer memory operations.