Arrays vs Linked Lists: Which Should You Actually Use?

Arrays and linked lists are two of the most fundamental ways to store a collection of data, and they show up constantly in technical interviews. Beginners often learn both without a clear sense of when to actually pick one over the other. Here's the practical breakdown.

How Arrays Work

An array stores elements in one continuous block of memory, sitting right next to each other. Because of this, you can jump directly to any position using its index, arr[5] takes exactly the same amount of time whether it's the first item you're accessing or the thousandth. This direct access is what makes arrays so fast for reading data at a known position.

The tradeoff: because arrays occupy contiguous memory, most languages require you to know the size upfront, or accept the cost of creating an entirely new, larger array and copying everything over when you need to grow it.

How Linked Lists Work

A linked list stores elements as separate nodes scattered anywhere in memory, with each node holding its data plus a pointer to the next node in the sequence. There's no requirement that the data sits next to each other, the nodes are connected purely through these pointers.

This means a linked list can grow or shrink freely without needing to reserve space upfront or copy the entire structure. Inserting a new element at the beginning of a linked list is fast, you just create a new node and point it to the old first node. Doing the same at the beginning of an array requires shifting every existing element over by one position.

The Access Speed Tradeoff

The major downside of linked lists shows up when you want to access an item at a specific position. Since there's no contiguous memory to jump into directly, you have to start at the first node and follow the pointers one at a time until you reach the position you want. For a list of a million items, finding the 500,000th item means following 500,000 pointers.

Arrays don't have this problem, jumping to arr[500000] is just as fast as arr[0], since the memory address can be calculated directly from the index.

When to Use Each

Reach for an array when you need fast, frequent access to elements by position, and the size of your collection is relatively stable or known ahead of time. Most everyday programming tasks, storing a list of scores, a set of coordinates, a fixed collection of items, fit this pattern well.

Reach for a linked list when you're frequently inserting or removing elements from the beginning or middle of your collection, and direct positional access isn't a priority. Linked lists are also the building block behind more advanced structures like stacks and queues.

The Practical Reality

In everyday application development, arrays (or their dynamic equivalents, like Python lists or Java's ArrayList) are used far more often, since most real-world tasks favor fast access over frequent insertion at arbitrary positions. Understanding linked lists matters most for technical interviews and for building a solid mental model of how data structures actually work under the hood.