Arrays (fixed and dynamic) in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a fixed-size array of 5 integers.

Blockchain / Solidity

int[[1]] numbers;

Drag options to blanks, or click blank then click option'

A0

B10

C5

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero or negative numbers for array size.

Forgetting to specify the size.

The fixed-size array must specify the size inside square brackets. Here, 5 means the array holds 5 integers.

2fill in blank

medium

Complete the code to declare a dynamic array of addresses.

Blockchain / Solidity

address[] public [1];

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Ausers

Bbalances

Cowners

Daccounts

Attempts:

3 left

💡 Hint

Common Mistakes

Using fixed-size brackets instead of empty brackets.

Using singular names for arrays.

Dynamic arrays are declared with empty square brackets []. The name 'users' is a common choice for an array of addresses.

3fill in blank

hard

Fix the error in the code to add an element to a dynamic array.

Blockchain / Solidity

users.[1](msg.sender);

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Apush

Bappend

Cadd

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'add' or 'append' which are not valid methods in Solidity.

Trying to assign directly without using a method.

In Solidity, the correct method to add an element to a dynamic array is 'push'.

4fill in blank

hard

Fill both blanks to declare a fixed-size array and assign a value to its first element.

Blockchain / Solidity

uint256[[1]] scores;
scores[[2]] = 100;

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A3

B0

C1

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 1 instead of 0 for the first element.

Using zero or negative number for array size.

The array size is 3, and the first element index is 0. So, scores[0] = 100 assigns 100 to the first element.

5fill in blank

hard

Fill all three blanks to create a dynamic array, add an element, and get its length.

Blockchain / Solidity

address[] public [1];

function addUser(address user) public {
    [1].[2](user);
}

function getUserCount() public view returns (uint) {
    return [1].[3];
}

Drag options to blanks, or click blank then click option'

Ausers

Bpush

Clength

Daccounts

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the array in different places.

Using 'append' or 'add' instead of 'push'.

Trying to call length as a function instead of a property.

The dynamic array is named 'users'. We add elements with 'push' and get the number of elements with 'length'.