What is DSA?

DSA combines data structures (ways to store and access data) and algorithms (step-by-step procedures). The goal is correct answers with predictable time and memory use as input size grows.

Data structures

• Array / vector — contiguous storage, O(1) index access
• Stack / queue — restricted access order (LIFO / FIFO)
• Hash map / set — average O(1) lookup by key
• Tree / heap / graph — hierarchical or networked relationships

Algorithms

• Searching — linear scan, binary search on sorted data
• Sorting — comparison sorts, when O(n log n) matters
• Traversal — BFS/DFS on trees and graphs
• Optimization patterns — greedy, dynamic programming, divide and conquer

Tiny example: sum an array

#include 

int main() {
    int arr[] = {3, 1, 4, 1, 5};
    int sum = 0;
    for (int x : arr) sum += x;
    std::cout << "sum = " << sum << "\n";
    return 0;
}

Important interview questions and answers

1. Q: Structure vs algorithm?
   A: A structure organizes data; an algorithm operates on it—often analyzed together for complexity.
2. Q: Why study DSA for jobs?
   A: Technical interviews and performance-sensitive backends test classic patterns and Big-O reasoning.

Self-check

1. Name four data structures from this lesson.
2. What does O(1) index access mean for arrays?

Tip: Separate structure (how data is stored) from algorithm (how you process it) in interview answers.