Lecture Notes: Introduction to Data Structures and Algorithms (DSA)

Welcome

• Host: Striver
• Introduction to the channel and its focus on programming and interview preparation.

Resources for Interview Preparation

• Strivers SD Sheet: A highly followed resource for interview preparation.
  • Contains 191 well-curated problems covering all DSA concepts.
  • Pre-requisite: Basic knowledge of DSA.
• Strivers A to Z DSA Course/Sheet: For beginners and intermediate users.
  • 455 curated steps with problem links.
  • Covers all important topics including dynamic programming.

Learning C++, Java, Python, and JavaScript

• Focus on mastering one programming language.
• Starting with C++ in this video.

C++ Basics

1. C++ Code Skeleton
   • General structure of a C++ program includes:
     • #include <iostream> (for input/output operations)
     • int main() function
     • return 0; to end the program.
2. Output: Use std::cout to print output.
   • Example: std::cout << "Hello, World!";
   • Use std::endl or to move to a new line.
3. Input: Use std::cin to take user input.
   • Example: std::cin >> x;
   • Can take multiple inputs: std::cin >> x >> y;

Data Types in C++

• Primitive Data Types:
  • int, long, long long, float, double for numbers.
  • char for single characters.
  • std::string for strings.
• Choosing Data Types:
  • Use int for numbers within certain ranges; switch to long or long long for larger numbers.
• Comments in C++:
  • Single-line comments: // comment
  • Multi-line comments: /* comment */

Control Structures

If-Else Statements

• Basic structure:
  • if (condition) { // code } else { // code }
• Nested if-else can be used to evaluate multiple conditions.

Switch Statement

• Useful for multiple conditions based on a single variable.
• Syntax:
  • switch(variable) { case value: // code; break; default: // code; }

Arrays

• One-Dimensional Arrays:
  • Used to store multiple items of the same data type.
  • Syntax: int arr[5];
• Accessing Elements:
  • Elements can be accessed using their index: arr[0], arr[1]...
• Two-Dimensional Arrays:
  • Useful for representing matrices.
  • Syntax: int arr[rows][columns];

Strings

• Strings are arrays of characters.
• Access elements using index like arrays.
• Length can be calculated using .size() or .length().

Loops

For Loop

• Used for executing code a specific number of times.
  • Syntax: for (initialization; condition; increment) { // code }

While Loop

• Continues until a specified condition is false.
  • Syntax: while (condition) { // code }

Do-While Loop

• Similar to while loop, but executes the code at least once.
  • Syntax: do { // code } while (condition);

Functions

• Purpose: Modularize code, increase readability, and avoid code repetition.
• Types of Functions:
  1. Void Functions: Do not return a value.
  2. Parameterized Functions: Accept parameters and perform operations.
  3. Return Functions: Return a value.

Pass by Value vs Pass by Reference

• Pass by Value: A copy of the variable is passed; changes in the function do not affect the original variable.
• Pass by Reference: The original variable is passed; changes in the function affect the original variable.

Conclusion

• Encourage viewers to like and subscribe to support the channel.
• Mention upcoming topics: Time Complexity - an important concept for interviews.
• Links to social media and further resources provided for learning.