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Lesson Content

Introduction to Data Structures & Algorithms

Data Structures and Algorithms (DSA) are fundamental concepts in computer science that help you write efficient, scalable code and solve complex problems.

What are Data Structures?

Data structures are ways of organizing and storing data in a computer so that it can be accessed and modified efficiently. Common examples include:

Arrays - Fixed-size collections of elements
Linked Lists - Dynamic collections connected by pointers
Stacks - Last-In-First-Out (LIFO) structures
Queues - First-In-First-Out (FIFO) structures
Trees - Hierarchical data structures
Graphs - Networks of connected nodes

What are Algorithms?

Algorithms are step-by-step procedures for solving problems. They define how data is processed, searched, sorted, and manipulated.

Why Learn DSA?

✅ Write efficient code that performs well
✅ Solve complex problems systematically
✅ Ace technical interviews at top companies
✅ Understand how software systems work
✅ Build scalable applications

Time Complexity (Big O Notation)

Big O notation describes how algorithm performance scales with input size:

O(1) - Constant time (instant)
O(log n) - Logarithmic (very fast)
O(n) - Linear (proportional to input)
O(n log n) - Linearithmic (efficient sorting)
O(n²) - Quadratic (slow for large inputs)

Example Code

Analyze the time complexity of different operations

// Example 1: O(1) - Constant time
function getFirst(arr) {
  return arr[0]; // Always takes same time
}

// Example 2: O(n) - Linear time
function findMax(arr) {
  let max = arr[0];
  for (let i = 1; i < arr.length; i++) {
    if (arr[i] > max) max = arr[i];
  }
  return max;
}

// Example 3: O(n²) - Quadratic time
function findDuplicates(arr) {
  let duplicates = [];
  for (let i = 0; i < arr.length; i++) {
    for (let j = i + 1; j < arr.length; j++) {
      if (arr[i] === arr[j]) duplicates.push(arr[i]);
    }
  }
  return duplicates;
}

let numbers = [3, 7, 2, 9, 5, 2, 7];
console.log('First element:', getFirst(numbers));
console.log('Max value:', findMax(numbers));
console.log('Duplicates:', findDuplicates(numbers));

Expected Output:

First element: 3
Max value: 9
Duplicates: [2, 7]

Study Tips

•Read the theory content thoroughly before practicing
•Review the example code to understand key concepts
•Proceed to the Practice tab when you're ready to code