> For the complete documentation index, see [llms.txt](https://cs4998.cornellblockchain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cs4998.cornellblockchain.org/introduction/hello-world-pt.-2/dynamic-arrays-and-strings/dynamic-arrays.md).

# Dynamic Arrays

Recall in Data Structures that we can declare a static array as follows:

```solidity
T[] arrayName = new T[](n);
```

where `T` is the type of the array. The good news is that defining a dynamic array is not that much different; below is the syntax for declaring a dynamic array:

```
T[] arrayName;
```

Declaring a dynamic array seems simple, but what about defining a dynamic array? Below is the syntax to define a dynamic array:

```solidity
T[] arrayName = [] // Insert array elements here
```

Since *dynamic arrays* can vary in size, we would ideally like to have functions available to us which allow us to grow/shrink our array. And indeed, Solidity provides us with such functions. 

* `array.push(x)`: pushes `x` to the back of `array`
* `array.pop()`: pops the last element of `array`

And like with static arrays, we can also index into dynamic arrays; it should be noted, however, that this can cause runtime errors if the user is attempting to index into an undefined location of a dynamic array.

{% hint style="info" %}

#### Dynamic Arrays in Memory?

As with mappings, dynamic arrays are reserved only for state variables; one cannot declare/define a new dynamic array variable within a function.
{% endhint %}


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