ppant · ppant · Jun 22, 2026
diff --git a/Arrays/Anagram_Check_manual_Sol.py → Arrays/AnagramCheckManualSol.py b/Arrays/Anagram_Check_manual_Sol.py → Arrays/AnagramCheckManualSol.py
diff --git a/Arrays/Anagram_Check_Sorted_Sol.py → Arrays/AnagramCheckSortedSol.py b/Arrays/Anagram_Check_Sorted_Sol.py → Arrays/AnagramCheckSortedSol.py
diff --git a/...yFindTheMissingElement_brute_force_sol.py → ...rrayFindTheMissingElementBruteForceSol.py b/...yFindTheMissingElement_brute_force_sol.py → ...rrayFindTheMissingElementBruteForceSol.py
diff --git a/...ayFindTheMissingElement_hash_table_sol.py → ...ArrayFindTheMissingElementHashTableSol.py b/...ayFindTheMissingElement_hash_table_sol.py → ...ArrayFindTheMissingElementHashTableSol.py
diff --git a/...issingElement_takingSumandSubtract_sol.py → Arrays/ArrayFindTheMissingElementSumSol.py b/...issingElement_takingSumandSubtract_sol.py → Arrays/ArrayFindTheMissingElementSumSol.py
diff --git a/Arrays/ArrayFindTheMissingElement_XOR_sol.py → Arrays/ArrayFindTheMissingElementXORSol.py b/Arrays/ArrayFindTheMissingElement_XOR_sol.py → Arrays/ArrayFindTheMissingElementXORSol.py
diff --git a/Arrays/README.md b/Arrays/README.md
@@ -4,10 +4,10 @@ This directory contains Python implementations of common array-based algorithms
 
 ## Contents
 
-- [Anagram Check (Sorted Solution)](Anagram_Check_Sorted_Sol.py): Checks if two strings are anagrams by comparing their sorted versions.
-- [Anagram Check (Manual Solution)](Anagram_Check_manual_Sol.py): Checks if two strings are anagrams using a hash table (dictionary) to count character frequencies.
-- [Array Find Missing Element (XOR Solution)](ArrayFindTheMissingElement_XOR_sol.py): Efficiently finds a missing element in a shuffled array using bitwise XOR.
-- [Array Find Missing Element (Brute Force Solution)](ArrayFindTheMissingElement_brute_force_sol.py): Finds a missing element by sorting both arrays and comparing them.
-- [Array Find Missing Element (Hash Table Solution)](ArrayFindTheMissingElement_hash_table_sol.py): Finds a missing element using a hash table (dictionary) to track element counts.
-- [Array Find Missing Element (Sum/Subtract Solution)](ArrayFindTheMissingElement_takingSumandSubtract_sol.py): Finds a missing element by calculating the difference between the sums of the two arrays.
+- [Anagram Check (Sorted Solution)](AnagramCheckSortedSol.py): Checks if two strings are anagrams by comparing their sorted versions. $O(n \log n)$
+- [Anagram Check (Manual Solution)](AnagramCheckManualSol.py): Checks if two strings are anagrams using a hash table (dictionary) to count character frequencies. $O(n)$
+- [Array Find Missing Element (XOR Solution)](ArrayFindTheMissingElementXORSol.py): Efficiently finds a missing element in a shuffled array using bitwise XOR. $O(n)$ time, $O(1)$ space.
+- [Array Find Missing Element (Brute Force Solution)](ArrayFindTheMissingElementBruteForceSol.py): Finds a missing element by sorting both arrays and comparing them. $O(n \log n)$
+- [Array Find Missing Element (Hash Table Solution)](ArrayFindTheMissingElementHashTableSol.py): Finds a missing element using a hash table (dictionary) to track element counts. $O(n)$
+- [Array Find Missing Element (Sum/Subtract Solution)](ArrayFindTheMissingElementSumSol.py): Finds a missing element by calculating the difference between the sums of the two arrays. $O(n)$
 - [Array Pair Sum Solution](ArrayPairSumSol.py): Finds all unique pairs in an array that sum up to a specific value $k$ using a set for $O(n)$ complexity.
diff --git a/deque/DequeImple.py → Deque/DequeImple.py b/deque/DequeImple.py → Deque/DequeImple.py
diff --git a/deque/README.md → Deque/README.md b/deque/README.md → Deque/README.md
@@ -4,4 +4,4 @@ This directory contains Python implementations of the Deque (Double-Ended Queue)
 
 ## Contents
 
-- [Deque Implementation](DequeImple.py): Basic implementation of a Deque using a Python list. Includes operations like `addFront`, `addRear`, `removeFront`, `removeRear`, `isEmpty`, and `size`.
+- [Deque Implementation](DequeImple.py): Basic implementation of a Deque using a Python list. Includes operations like `addFront`, `addRear`, `removeFront`, `removeRear`, `isEmpty`, and `size`. Time complexity: `addFront`/`removeFront` $O(1)$, `addRear`/`removeRear` $O(n)$ due to list shifting.
diff --git a/Error-debug/README.md b/Error-debug/README.md
diff --git a/Error-debug/ErrorExceptions.py → ErrorHandling/ErrorExceptions.py b/Error-debug/ErrorExceptions.py → ErrorHandling/ErrorExceptions.py
diff --git a/ErrorHandling/README.md b/ErrorHandling/README.md
@@ -0,0 +1,7 @@
+# Error Handling
+
+This directory contains examples demonstrating error handling and debugging in Python.
+
+## Contents
+
+- [Error and Exceptions](ErrorExceptions.py): Demonstrates `try`, `except`, `else`, and `finally` blocks for robust error handling.
diff --git a/GraphAlgorithms/README.md b/GraphAlgorithms/README.md
@@ -1,12 +1,12 @@
 # Graph Algorithms
 
-This directory contains Python implementations of common graph-based algorithms and data structures.
+This directory contains Python implementations of common graph algorithms.
 
 ## Contents
 
-- [Adjacency List Implementation](AdjacencyListGraphImple.py): Implements the Graph Abstract Data Type (ADT) using an adjacency list (dictionaries in Python). Includes `Vertex` and `Graph` classes.
-- [Breadth First Search (BFS)](BFS.py): Implements BFS to solve the Word Ladder problem, finding the shortest transformation path between words.
-- [General Depth First Search (DFS)](DFSGeneral.py): Provides a general implementation of DFS, including discovery and finish times for vertices.
-- [DFS - Knight's Tour Problem](DFSImpleTheKnightsTourProblem.py): Another implementation of DFS specifically tailored to the Knight's Tour puzzle.
-- [The Knight's Tour Problem](TheKnightsTourProblem.py): Focuses on generating the knight's move graph and solving the tour using DFS and backtracking.
-- [Word Ladder Problem](WordLadderProblem.py): Specifically focuses on building the word ladder graph where edges connect words that differ by only one letter.
+- [Adjacency List Graph Implementation](AdjacencyListGraphImple.py): Implementation of the Graph Abstract Data Type using an adjacency list.
+- [Breadth First Search (BFS)](BFS.py): Implementation of BFS, applied to the Word Ladder problem. $O(V+E)$
+- [Depth First Search (DFS)](DFSGeneral.py): General implementation of Depth First Search. $O(V+E)$
+- [The Knight's Tour Problem (Graph Generation)](TheKnightsTourProblem.py): Building a graph representing all possible legal moves on a chessboard.
+- [The Knight's Tour Problem (DFS Solution)](DFSImpleTheKnightsTourProblem.py): Solving the Knight's Tour problem using DFS. $O(k^N)$
+- [Word Ladder Problem](WordLadderProblem.py): Implementation of the Word Ladder problem using graphs.
diff --git a/LinkedLists/README.md b/LinkedLists/README.md
@@ -1,11 +1,11 @@
 # Linked Lists
 
-This directory contains Python implementations of various types of linked lists and related algorithms.
+This directory contains Python implementations of linked list data structures and related problems.
 
 ## Contents
 
-- [Singly Linked List Implementation](SingleLinkedListImple.py): Basic implementation of a singly linked list node and basic linkage.
-- [Doubly Linked List Implementation](DoublyLinkedListImple.py): Basic implementation of a doubly linked list node with `prev` and `next` pointers.
-- [Singly Linked List Cycle Check](SinglyLinkedListCycleCheckImple.py): Implements Floyd's Cycle-Finding Algorithm (two pointers) to detect cycles in a linked list.
-- [Linked List Reversal](LinkedListReversal.py): Reverses a singly linked list in-place in $O(n)$ time.
-- [Nth to Last Node](LinkedListNthToLastNode.py): Finds the $n$-th to last node in a singly linked list using two pointers.
+- [Singly Linked List Implementation](SinglyLinkedListImple.py): Basic implementation of a singly linked list. $O(1)$ for insertion/deletion at the head.
+- [Doubly Linked List Implementation](DoublyLinkedListImple.py): Basic implementation of a doubly linked list. $O(1)$ for insertion/deletion at both ends.
+- [Singly Linked List Cycle Check](SinglyLinkedListCycleCheckImple.py): Implementation of Floyd's cycle-finding algorithm to detect cycles in a linked list. $O(n)$
+- [Linked List Reversal](LinkedListReversal.py): In-place reversal of a singly linked list. $O(n)$
+- [Linked List Nth to Last Node](LinkedListNthToLastNode.py): Finding the $n$-th to last node in a singly linked list. $O(n)$
diff --git a/LinkedLists/SinglyLinkedListCycleCheckImple.py b/LinkedLists/SinglyLinkedListCycleCheckImple.py
@@ -19,10 +19,10 @@ def __init__(self, value):
         self.value = value
         self.nextnode = None
 
-    def cycle_check(node):
-        # Set two pointers initialize to passed node
-        pt1 = node
-        pt2 = node
+    def cycle_check(self):
+        # Set two pointers initialize to self
+        pt1 = self
+        pt2 = self
         # loop through end of the list
         while pt2 != None and pt2.nextnode != None:
             pt1 = pt1.nextnode
@@ -46,12 +46,9 @@ def cycle_check(node):
 print (b.value)
 print (c.value)
 
-# Since cycle_check is a method but it doesn't use self and is defined inside class
-# it should be called on an instance or changed to static method.
-# In its current definition it behaves like a regular method but is missing 'self'.
-# Actually it is defined as def cycle_check(node): which means it takes one arg.
-# If called as LinkedListNode.cycle_check(a) it should work if it was just a function.
-
-print(a.cycle_check())
-
+# Test with cycle
+print(f"Cycle detected (expected True): {a.cycle_check()}")
 
+# Test without cycle
+c.nextnode = None
+print(f"Cycle detected (expected False): {a.cycle_check()}")
diff --git a/LinkedLists/SingleLinkedListImple.py → LinkedLists/SinglyLinkedListImple.py b/LinkedLists/SingleLinkedListImple.py → LinkedLists/SinglyLinkedListImple.py
diff --git a/Queues/README.md b/Queues/README.md
@@ -1,8 +1,8 @@
 # Queues
 
-This directory contains Python implementations of the Queue data structure.
+This directory contains Python implementations of the Queue (First-In-First-Out) data structure.
 
 ## Contents
 
-- [Queue Implementation](QueueImple.py): Basic implementation of a FIFO (First-In-First-Out) queue using a Python list. Includes `enqueue`, `dequeue`, `isEmpty`, and `size` methods.
-- [Queue with Two Stacks](QueueWith2StacksImple.py): Implements a queue using two stacks (represented by Python lists) to achieve FIFO behavior.
+- [Queue Implementation](QueueImple.py): Basic implementation of a Queue using a Python list. `enqueue` $O(n)$, `dequeue` $O(1)$.
+- [Queue with 2 Stacks](QueueWith2StacksImple.py): Implementation of a Queue using two stacks. $O(1)$ amortized for both `enqueue` and `dequeue`.
diff --git a/README.md b/README.md
@@ -67,7 +67,7 @@ Most scripts in this repository are standalone and can be executed directly:
 
 ```bash
 # Run any Python script
-python3 Arrays/Anagram_Check_Sorted_Sol.py
+python3 Arrays/AnagramCheckSortedSol.py
 
 # Or run from the repo root
 python3 Sorting/BubbleSortImple.py
@@ -80,15 +80,15 @@ python3 Sorting/BubbleSortImple.py
 ```
 .
 ├── Arrays/              # 🔤 Array-based problems and algorithms
-├── Error-debug/         # ⚠️ Error handling and debugging examples
+├── Deque/               # 🔄 Double-ended queue
+├── ErrorHandling/       # ⚠️ Error handling and debugging examples
 ├── GraphAlgorithms/     # 🗺️ Graph traversal (BFS, DFS) and pathfinding
 ├── LinkedLists/         # 🔗 Singly and Doubly Linked Lists
 ├── Queues/              # 📦 Queue implementations (FIFO)
 ├── Recursion/           # 🔀 Recursive problems and Dynamic Programming
 ├── Sorting/             # 📊 Common sorting algorithms
 ├── Stacks/              # 📚 Stack implementations and applications
 ├── Trees/               # 🌳 Binary Trees, BSTs, Heaps, and Traversals
-├── deque/               # 🔄 Double-ended queue
 ├── CONTRIBUTING.md      # 🤝 Contribution guidelines
 ├── LICENSE              # 📄 MIT License
 └── README.md            # 📖 This file
@@ -100,21 +100,21 @@ python3 Sorting/BubbleSortImple.py
 
 ### Arrays 🔤
 Common array-based algorithms and manipulations.
-- [Anagram Check](Arrays/): [Sorted](Arrays/Anagram_Check_Sorted_Sol.py) & [Manual](Arrays/Anagram_Check_manual_Sol.py) solutions
+- [Anagram Check](Arrays/): [Sorted](Arrays/AnagramCheckSortedSol.py) & [Manual](Arrays/AnagramCheckManualSol.py) solutions
 - [Array Pair Sum](Arrays/ArrayPairSumSol.py): Find pairs that sum to $k$
-- [Find Missing Element](Arrays/): [XOR](Arrays/ArrayFindTheMissingElement_XOR_sol.py), [Brute Force](Arrays/ArrayFindTheMissingElement_brute_force_sol.py), [Hash Table](Arrays/ArrayFindTheMissingElement_hash_table_sol.py), & [Sum](Arrays/ArrayFindTheMissingElement_takingSumandSubtract_sol.py) approaches
+- [Find Missing Element](Arrays/): [XOR](Arrays/ArrayFindTheMissingElementXORSol.py), [Brute Force](Arrays/ArrayFindTheMissingElementBruteForceSol.py), [Hash Table](Arrays/ArrayFindTheMissingElementHashTableSol.py), & [Sum](Arrays/ArrayFindTheMissingElementSumSol.py) approaches
 
 ### Linked Lists 🔗
 Implementations and problems involving linked structures.
-- [Singly Linked List](LinkedLists/SingleLinkedListImple.py) & [Doubly Linked List](LinkedLists/DoublyLinkedListImple.py)
+- [Singly Linked List](LinkedLists/SinglyLinkedListImple.py) & [Doubly Linked List](LinkedLists/DoublyLinkedListImple.py)
 - [Cycle Detection](LinkedLists/SinglyLinkedListCycleCheckImple.py): Detect cycles using two pointers (Floyd's algorithm)
 - [Reverse Linked List](LinkedLists/LinkedListReversal.py): In-place reversal
 - [Nth to Last Node](LinkedLists/LinkedListNthToLastNode.py): Find the $n$-th node from the end
 
 ### Stacks 📚
 LIFO (Last-In-First-Out) data structures.
 - [Stack Implementation](Stacks/StackImple.py): Basic operations (push, pop, peek)
-- [Balanced Parentheses](Stacks/BalanceParenthlessCheckImple.py): Check for balanced brackets using a stack
+- [Balanced Parentheses](Stacks/BalanceParenthesesCheckImple.py): Check for balanced brackets using a stack
 
 ### Queues 📦
 FIFO (First-In-First-Out) data structures.
@@ -123,7 +123,7 @@ FIFO (First-In-First-Out) data structures.
 
 ### Deque 🔄
 Double-ended queue operations.
-- [Deque Implementation](deque/DequeImple.py): Operations at both ends
+- [Deque Implementation](Deque/DequeImple.py): Operations at both ends
 
 ### Trees 🌳
 Hierarchical data structures.
@@ -133,7 +133,7 @@ Hierarchical data structures.
 - [Binary Heap](Trees/BinaryHeapImple.py): Min-heap implementation
 - [Tree Traversals](Trees/TreeLevelOrderPrintImple.py): Level order (BFS) printing
 - [Trim BST](Trees/TrimBinarySearchTreeImple.py): Keep nodes within a range
-- [Tree Representations](Trees/): [Nodes & References](Trees/TreeRepresentationWithNodesReferences.py) & [List of Lists](Trees/buildTreeTest.py)
+- [Tree Representations](Trees/): [Nodes & References](Trees/TreeRepresentationWithNodesReferences.py) & [List of Lists](Trees/BuildTreeTest.py)
 
 ---
 
@@ -144,7 +144,7 @@ Algorithms for arranging elements in order.
 - [Bubble Sort](Sorting/BubbleSortImple.py) - $O(n^2)$
 - [Selection Sort](Sorting/SelectionSortImple.py) - $O(n^2)$
 - [Insertion Sort](Sorting/InsertionSortImple.py) - $O(n^2)$
-- [Shell Sort](Sorting/ShellSortImple.py) - $O(n \log n)$
+- [Shell Sort](Sorting/ShellSortImple.py) - $O(n^2)$
 - [Merge Sort](Sorting/MergeSortImple.py) - $O(n \log n)$
 - [Quick Sort](Sorting/QuickSortImple.py) - $O(n \log n)$ average
 
@@ -168,7 +168,7 @@ Algorithms for graph traversal and pathfinding.
 
 ## ⚠️ Error Handling & Debugging
 
-- [Error and Exceptions](Error-debug/ErrorExceptions.py): Demonstrates `try`, `except`, `else`, and `finally` blocks for robust error handling.
+- [Error and Exceptions](ErrorHandling/ErrorExceptions.py): Demonstrates `try`, `except`, `else`, and `finally` blocks for robust error handling.
 
 ---
 
@@ -215,7 +215,7 @@ New to DSA? Follow this recommended order:
 ## 🔮 Roadmap
 
 - [ ] Add more graph algorithms (Dijkstra, Bellman-Ford)
-- [ ] Include complexity analysis for each solution
+- [x] Include complexity analysis for each solution
 - [ ] Add interactive examples/visualizations
 - [ ] Create a difficulty level classification
 - [ ] Add more test cases

diff --git a/Recursion/README.md b/Recursion/README.md
@@ -4,18 +4,13 @@ This directory contains Python implementations of problems solved using recursio
 
 ## Contents
 
-### Fibonacci Sequence
-- [Fibonacci (Iterative)](FibonacciSeqIterative.py): Iterative implementation of the Fibonacci sequence.
-- [Fibonacci (Recursive)](FibonacciSeqRecursion.py): Simple recursive implementation of the Fibonacci sequence.
-- [Fibonacci (Dynamic Programming)](FibonacciSeqDynamic.py): Optimized Fibonacci sequence using memoization.
-
-### Coin Change Problem
-- [Coin Change (Recursive)](CoinChangeProblemRecursion.py): Basic recursive solution to find the minimum number of coins for change.
-- [Coin Change (Dynamic Programming)](CoinChangeProblemDynamic.py): Optimized solution to the coin change problem using dynamic programming.
-
-### Other Recursive Problems
-- [Cumulative Sum](RecursionCumulativeSum.py): Computes the cumulative sum from 0 to $n$ recursively.
-- [Reverse a String](RecursionReverseStr.py): Reverses a string using recursive calls.
-- [String Permutations](RecursionStrPermutation.py): Generates all possible permutations of a given string.
-- [Sum of Digits](RecursionSumOfDigits.py): Calculates the sum of all individual digits in an integer recursively.
-- [Word Split](RecursionWordSplit.py): Determines if a string can be split into words from a given list.
+- [Coin Change Problem (Recursive)](CoinChangeProblemRecursion.py): Solving the coin change problem using pure recursion. Exponential complexity.
+- [Coin Change Problem (Dynamic Programming)](CoinChangeProblemDynamic.py): Solving the coin change problem using dynamic programming (memoization). $O(n \cdot m)$ where $n$ is target and $m$ is number of coins.
+- [Fibonacci Sequence (Recursive)](FibonacciSeqRecursion.py): Generating Fibonacci numbers using recursion. $O(2^n)$
+- [Fibonacci Sequence (Iterative)](FibonacciSeqIterative.py): Generating Fibonacci numbers using iteration. $O(n)$
+- [Fibonacci Sequence (Dynamic Programming)](FibonacciSeqDynamic.py): Generating Fibonacci numbers using dynamic programming. $O(n)$
+- [Recursion Cumulative Sum](RecursionCumulativeSum.py): Calculating cumulative sum using recursion. $O(n)$
+- [Recursion Reverse String](RecursionReverseStr.py): Reversing a string using recursion. $O(n)$
+- [Recursion String Permutation](RecursionStrPermutation.py): Generating all permutations of a string using recursion. $O(n!)$
+- [Recursion Sum of Digits](RecursionSumOfDigits.py): Calculating the sum of digits using recursion. $O(\log_{10} n)$
+- [Recursion Word Split](RecursionWordSplit.py): Splitting a string into words based on a dictionary using recursion.
diff --git a/Sorting/README.md b/Sorting/README.md
@@ -5,8 +5,8 @@ This directory contains Python implementations of various sorting algorithms wit
 ## Contents
 
 - [Bubble Sort](BubbleSortImple.py): Implementation of Bubble Sort with $O(n^2)$ complexity.
-- [Selection Sort](SelectionSortImple.py): Implementation of Selection Sort, improving on Bubble Sort by making only one exchange per pass.
-- [Insertion Sort](InsertionSortImple.py): Implementation of Insertion Sort, maintaining a sorted sublist.
-- [Shell Sort](ShellSortImple.py): Implementation of Shell Sort (diminishing increment sort), improving on Insertion Sort.
+- [Selection Sort](SelectionSortImple.py): Implementation of Selection Sort, improving on Bubble Sort by making only one exchange per pass. $O(n^2)$
+- [Insertion Sort](InsertionSortImple.py): Implementation of Insertion Sort, maintaining a sorted sublist. $O(n^2)$
+- [Shell Sort](ShellSortImple.py): Implementation of Shell Sort (diminishing increment sort), improving on Insertion Sort. $O(n^2)$ worst-case.
 - [Merge Sort](MergeSortImple.py): A recursive "divide and conquer" algorithm with $O(n \log n)$ complexity.
-- [Quick Sort](QuickSortImple.py): Implementation of Quick Sort (partition exchange sort), using divide and conquer in-place.
+- [Quick Sort](QuickSortImple.py): Implementation of Quick Sort (partition exchange sort), using divide and conquer in-place. $O(n \log n)$ average.
diff --git a/Stacks/BalanceParenthlessCheckImple.py → Stacks/BalanceParenthesesCheckImple.py b/Stacks/BalanceParenthlessCheckImple.py → Stacks/BalanceParenthesesCheckImple.py
diff --git a/Stacks/README.md b/Stacks/README.md
@@ -1,8 +1,8 @@
 # Stacks
 
-This directory contains Python implementations of the Stack data structure and its applications.
+This directory contains Python implementations of the Stack (Last-In-First-Out) data structure.
 
 ## Contents
 
-- [Stack Implementation](StackImple.py): Basic implementation of a LIFO (Last-In-First-Out) stack using a Python list. Includes `push`, `pop`, `peek`, `isEmpty`, and `size` methods.
-- [Balanced Parentheses Check](BalanceParenthlessCheckImple.py): Uses a stack to check if a string of opening and closing parentheses (round, square, and curly) is balanced.
+- [Stack Implementation](StackImple.py): Basic implementation of a Stack with push, pop, peek, isEmpty, and size operations. $O(1)$
+- [Balanced Parentheses Check](BalanceParenthesesCheckImple.py): Using a stack to check if a string of parentheses is balanced. $O(n)$
diff --git a/Trees/buildTreeTest.py → Trees/BuildTreeTest.py b/Trees/buildTreeTest.py → Trees/BuildTreeTest.py
Original file line number	Diff line number	Diff line change
Expand Up		@@ -4,4 +4,4 @@ This directory contains Python implementations of the Deque (Double-Ended Queue)

		## Contents

		- [Deque Implementation](DequeImple.py): Basic implementation of a Deque using a Python list. Includes operations like `addFront`, `addRear`, `removeFront`, `removeRear`, `isEmpty`, and `size`.
		- [Deque Implementation](DequeImple.py): Basic implementation of a Deque using a Python list. Includes operations like `addFront`, `addRear`, `removeFront`, `removeRear`, `isEmpty`, and `size`. Time complexity: `addFront`/`removeFront` $O(1)$, `addRear`/`removeRear` $O(n)$ due to list shifting.