Variable packing in Blockchain / Solidity - Time & Space Complexity

Time Complexity: Variable packing

O(n)

Understanding Time Complexity

When working with blockchain, how we store variables can affect how fast our code runs.

We want to see how packing variables together changes the work the program does.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

struct Data {
  uint128 a;
  uint128 b;
}

function storeData(Data[] memory dataList) public {
  for (uint i = 0; i < dataList.length; i++) {
    // store each packed data item
  }
}
    

This code stores a list of data items where two 128-bit numbers are packed together in one struct.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Loop over each element in the dataList array.
• How many times: Once for each item in the input list (n times).

How Execution Grows With Input

As the number of data items grows, the loop runs more times, doing more work.

Input Size (n)	Approx. Operations
10	10 loop steps
100	100 loop steps
1000	1000 loop steps

Pattern observation: The work grows directly with the number of items.

Final Time Complexity

Time Complexity: O(n)

This means the time to run grows in a straight line as the input size grows.

Common Mistake

[X] Wrong: "Packing variables makes the loop run faster and changes time complexity."

[OK] Correct: Packing reduces storage size but the loop still runs once per item, so time grows the same way.

Interview Connect

Understanding how variable packing affects performance shows you know both storage and execution costs, a useful skill in blockchain development.

Self-Check

"What if the dataList contained nested arrays inside each item? How would the time complexity change?"