Gas optimization with storage in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a storage variable for an unsigned integer.

Blockchain / Solidity

uint256 [1];

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

Amemory

Bstorage

Ctemp

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'memory' or 'storage' as variable names.

Leaving the variable name blank.

The variable name should be count. memory and storage are data location keywords, not variable names.

2fill in blank

medium

Complete the code to declare a fixed-size array in storage.

Blockchain / Solidity

uint256[[1]] numbers;

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

Alength

B5

Ccount

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names instead of a number for array size.

Leaving the size blank.

The array size must be a number literal like 5. Variable names like size or length are not valid here.

3fill in blank

hard

Fix the error in the function to reduce gas by using a local variable for storage reads.

Blockchain / Solidity

function getSum() public view returns (uint256) {
    uint256 [1] = a + b + c;
    return sum;
}

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

Asum

Btotal

Cresult

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than the return statement.

Not using a local variable at all.

The local variable should be named sum to match the return statement and reduce repeated storage reads.

4fill in blank

hard

Fill both blanks to optimize storage writes by caching in a local variable.

Blockchain / Solidity

function increment() public {
    uint256 [1] = [2];
    [2] = [1] + 1;
}

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

Atemp

Bcounter

Ccount

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Writing directly to storage multiple times.

Using the same name for both variables.

Cache the storage variable counter in a local variable temp, then update counter after incrementing.

5fill in blank

hard

Fill all three blanks to create a mapping and update it efficiently.

Blockchain / Solidity

mapping(address => uint256) public [1];

function updateBalance(address user, uint256 amount) public {
    uint256 [2] = [3][user];
    [3][user] = [2] + amount;
}

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

Abalances

BcurrentBalance

Cbalance

Dtemp

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names.

Not caching the balance before updating.

The mapping is named balances. Cache the user's balance in currentBalance and update balances[user] after adding amount.