Arrays (fixed and dynamic) in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a fixed-size array in blockchain programming?

A fixed-size array is an array with a set number of elements that cannot change after declaration. Its size is known at compile time.

beginner

How does a dynamic array differ from a fixed array?

A dynamic array can grow or shrink during runtime, allowing flexible storage of elements, unlike fixed arrays which have a constant size.

beginner

In Solidity, how do you declare a fixed-size array of 5 unsigned integers?

You declare it like this: uint[5] fixedArray; This creates an array that holds exactly 5 unsigned integers.

beginner

How do you add an element to a dynamic array in Solidity?

You use the push() method. For example: dynamicArray.push(10); adds the value 10 to the end of the array.

intermediate

Why are fixed-size arrays more gas efficient than dynamic arrays in blockchain?

Fixed-size arrays have a known size at compile time, so they use less storage and gas. Dynamic arrays require extra gas to manage resizing and storage.

Which of the following is a correct way to declare a dynamic array of addresses in Solidity?

A address[] dynamicAddresses;

B address[5] dynamicAddresses;

C dynamic address[];

D address dynamic[];

Option A declares a dynamic array of addresses correctly using address[].

What happens if you try to add an element beyond the fixed size of a fixed array?

A The element is added successfully.

B It overwrites the last element.

C It causes a compile-time error.

D It automatically resizes the array.

Fixed-size arrays cannot change size, so adding beyond their size causes a compile-time error.

Which method is used to remove the last element from a dynamic array in Solidity?

A delete()

B remove()

C clear()

D pop()

The pop() method removes the last element from a dynamic array.

Why might you choose a fixed-size array over a dynamic array in a smart contract?

A To allow flexible data storage.

B To reduce gas costs and improve performance.

C Because fixed arrays can grow automatically.

D Because dynamic arrays are not supported.

Fixed-size arrays use less gas and are more efficient when the size is known and constant.

How do you access the third element in a Solidity array named myArray?

A myArray[2]

B myArray[3]

C myArray.get(3)

D myArray.element(3)

Array indexing starts at 0, so the third element is at index 2.

Explain the difference between fixed-size and dynamic arrays in blockchain smart contracts.

Think about how the array size changes and gas costs.

Describe how you would declare and use a dynamic array in Solidity.

Focus on declaration, adding, removing, and accessing elements.