Dsa Progess


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Things To Remember

    โœ… Understand the logic, donโ€™t just memorize code. ๐Ÿงฑ Always begin with brute force, then optimize. โœ๏ธ Practice coding on paperโ€”train for interviews. โฑ๏ธ Time yourself like in real coding rounds. ๐Ÿž Debug smartlyโ€”use print and dry runs. ๐Ÿ” Revise tricky questions every week. ๐Ÿ“Œ Never skip edge test cases. ๐Ÿ” Reflect on alternate solutions after solving. ๐Ÿš€ Solve fewer, but with full depth. โ›” Donโ€™t rush to watch the solutionโ€”try first.

Daily Basiss Dsa Motivation

ARRAY

๐Ÿ”ข Quick Revise โ€“ Arrays

โœ… What is an Array

  • A linear data structure.
  • Stores elements in contiguous memory.
  • Accessed via indexing (0-based).
  • Stores same type of elements.

๐Ÿง  Key Characteristics:

  • Fixed size (static arrays).
  • Elements stored in sequence.
  • Direct access via index: arr[i].
  • Efficient read, costly middle insert/delete.

โฑ๏ธ Time Complexities:

  • Access: O(1)
  • Update: O(1)
  • Search: O(n)
  • Insert/Delete (middle): O(n)

๐Ÿงช Important Techniques:

  • Two Pointers โ€“ optimize search & traversal.
  • Sliding Window โ€“ handle fixed or variable size subarrays.
  • Prefix Sum โ€“ for range-based calculations.
  • Kadaneโ€™s Algorithm โ€“ max subarray sum.
  • In-place Swapping / Reversal โ€“ optimize space.
  • Sorting + Binary Search โ€“ combo for many problems.

๐Ÿงฐ Language Helpers:

  • C++: vector, .size(), sort().
  • JavaScript: push(), splice(), map(), filter().

STRING

๐Ÿงต Quick Revise โ€“ Strings

โœ… What is a String

  • A sequence of characters.
  • Stored as arrays in memory.
  • Strings are immutable in most languages.
  • Can be manipulated using standard libraries.

๐Ÿง  Key Characteristics:

  • Fixed or dynamic in size (depends on language).
  • 0-based indexing for character access.
  • Immutability in Java, Python (new copy on change).
  • Character operations like comparison, slicing, appending.

โฑ๏ธ Time Complexities:

  • Access: O(1)
  • Concatenation: O(n)
  • Search: O(n)
  • Substring: O(k) [k = substring length]

๐Ÿงช Important Techniques:

  • Two Pointers โ€“ useful in palindrome and pattern match.
  • Sliding Window โ€“ for substring search, longest unique substring.
  • Hashing โ€“ frequency/count maps for anagram problems.
  • Trie โ€“ prefix matching, auto-complete.
  • KMP / Z Algorithm โ€“ advanced pattern matching.

๐Ÿงฐ Language Helpers:

  • C++: string, substr(), compare(), find().
  • JavaScript: length, split(), indexOf(), slice(), includes().
  • Python: strip(), join(), find(), slicing, in-operator.

SEARCHING

๐Ÿ” Quick Revise โ€“ Searching

โœ… What is Searching?

  • Searching is the process of finding a target element within a data structure.
  • Two main types: Linear Search and Binary Search.
  • Binary Search works only on sorted data.

๐Ÿง  Key Concepts:

  • Linear Search: Sequential scan (O(n)).
  • Binary Search: Divide & conquer (O(log n)).
  • Variants: First/Last Occurrence, Count of Occurrences.
  • Advanced: Search in Rotated Array, Binary Search on Answer.

โฑ๏ธ Time Complexities:

  • Linear Search: O(n)
  • Binary Search: O(log n)

๐Ÿงฐ Language Helpers:

  • C++: std::binary_search(), lower_bound(), upper_bound()
  • JavaScript: indexOf(), findIndex(), includes()

SORTING

๐Ÿ”ƒ Quick Revise โ€“ Sorting

โœ… Why Sorting is Important?

  • Sorting arranges data in a particular order (ascending/descending).
  • It is often used before searching, binary search, or optimization problems.

๐Ÿง  Key Sorting Algorithms:

  • Bubble Sort โ€“ swap adjacent elements repeatedly.
  • Selection Sort โ€“ select minimum & place at front.
  • Insertion Sort โ€“ build sorted part one element at a time.
  • Merge Sort โ€“ divide & merge (recursive).
  • Quick Sort โ€“ choose pivot and partition.

โฑ๏ธ Time Complexities:

  • Bubble, Insertion, Selection โ€“ O(nยฒ)
  • Merge, Quick (Avg) โ€“ O(n log n)

RECURSION & BACKTRACKING

๐Ÿ”„ Quick Revise โ€“ Recursion & Backtracking

โœ… Key Concepts

  • Recursion: Function calling itself for sub-problems.
  • Base Case: Stopping condition for recursion.
  • Backtracking: Explore all paths, undo steps when needed.
  • Used in combinations, permutations, pathfinding, N-Queens, etc.

๐Ÿง  Tips

  • Always define base case.
  • Dry run small input.
  • Use recursion tree to debug.

STACK

๐Ÿ“š Quick Revise โ€“ Stack

โœ… What is a Stack?

  • Linear data structure that follows LIFO (Last-In-First-Out).
  • Insertion (push) and deletion (pop) at the same end (top).

๐Ÿ”ง Applications of Stack:

  • Expression evaluation and syntax parsing.
  • Undo mechanisms in editors.
  • Backtracking problems (recursion, DFS).

QUEUE

๐Ÿšฆ Quick Revise โ€“ Queue

โœ… What is a Queue?

  • Linear data structure following FIFO (First-In-First-Out).
  • Insertion at rear, deletion from front.

๐Ÿ”ง Applications of Queue:

  • Task scheduling, CPU scheduling.
  • Print queues, messaging systems.
  • Level order traversal in trees.

LINKED LIST

๐Ÿ”— Quick Revise โ€“ Linked List

โœ… What is a Linked List?

  • Linear data structure where elements (nodes) point to the next.
  • Efficient insert/delete, dynamic size.
  • Types: Singly, Doubly, Circular.

๐Ÿ“Œ Key Operations:

  • Insertion & Deletion at head, tail, middle.
  • Finding middle, detecting/removing loops.
  • Reversing list, merging, sorting, etc.

BINARY TREE

๐ŸŒณ Quick Revise โ€“ Binary Tree

โœ… What is a Binary Tree?

  • Each node has at most 2 children: left and right.
  • Special cases: full, perfect, complete, skewed trees.

๐Ÿ“Œ Applications:

  • Expression parsing, hierarchical storage, routing tables.
  • Foundations of BST, Heaps, Segment Trees.

BINARY SEARCH TREE

๐ŸŒฒ Quick Revise โ€“ Binary Search Tree

โœ… What is a BST?

  • A binary tree where left < root < right.
  • All left subtree nodes are smaller, right are greater.
  • Provides efficient search, insert, delete.

๐Ÿ“Œ Key Uses:

  • Dynamic sets, searching, and sorting.
  • Foundation for AVL, Red-Black Trees.

GRAPH

๐ŸŒ Quick Revise โ€“ Graphs

โœ… What is a Graph?

  • A collection of nodes (vertices) and edges.
  • Can be directed/undirected, weighted/unweighted.
  • Represented using adjacency list or matrix.

๐Ÿ”ง Traversal Techniques:

  • BFS โ€“ Level-order traversal using queue.
  • DFS โ€“ Depth-first using stack/recursion.
  • Cycle detection (DFS/Union Find).

DYNAMIC PROGRAMMING

โšก Quick Revise โ€“ Dynamic Programming

โœ… What is Dynamic Programming?

  • Solving problems by breaking them into overlapping subproblems.
  • Use of memoization or tabulation to store results.
  • Reduces time complexity from exponential to polynomial.

๐Ÿง  Common Types:

  • 0/1 Knapsack, Subset Sum
  • Fibonacci, Climbing Stairs
  • Longest Common Subsequence (LCS)
  • Matrix DP, DP on Trees/Graphs

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