Working with JSON files in C Sharp (C#) - Time & Space Complexity

Time Complexity: Working with JSON files

O(n)

Understanding Time Complexity

When working with JSON files in C#, it's important to understand how the time to read or write data grows as the file size increases.

We want to know how the program's running time changes when the JSON file gets bigger.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

using System.Text.Json;
using System.IO;
using System.Collections.Generic;

string jsonString = File.ReadAllText("data.json");
var data = JsonSerializer.Deserialize<List<Person>>(jsonString);

foreach (var person in data)
{
    Console.WriteLine(person.Name);
}
    

This code reads a JSON file, converts it into a list of objects, and then prints each person's name.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Looping through each person in the list to print their name.
• How many times: Once for each person in the JSON data (n times).

How Execution Grows With Input

As the number of people in the JSON file grows, the time to read and print their names grows roughly the same way.

Input Size (n)	Approx. Operations
10	About 10 reads and prints
100	About 100 reads and prints
1000	About 1000 reads and prints

Pattern observation: The work grows directly with the number of items; doubling the data doubles the work.

Final Time Complexity

Time Complexity: O(n)

This means the time to process the JSON file grows in a straight line with the number of items inside it.

Common Mistake

[X] Wrong: "Reading a JSON file always takes the same time no matter how big it is."

[OK] Correct: The bigger the file and the more items inside, the longer it takes to read and process each item.

Interview Connect

Understanding how reading and processing JSON scales helps you write efficient programs and answer questions about data handling in interviews.

Self-Check

"What if we changed the code to only read and print the first 10 items regardless of file size? How would the time complexity change?"