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14 changes: 7 additions & 7 deletions Arrays/README.md
Original file line number Diff line number Diff line change
Expand Up @@ -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.
- [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.
- [Anagram Check (Sorted Solution)](AnagramCheckSortedSol.py): Checks if two strings are anagrams by comparing their sorted versions. Time Complexity: $O(n \log n)$.
- [Anagram Check (Manual Solution)](AnagramCheckManualSol.py): Checks if two strings are anagrams using a hash table (dictionary) to count character frequencies. Time Complexity: $O(n)$.
- [Array Find Missing Element (XOR Solution)](ArrayFindTheMissingElementXORSol.py): Efficiently finds a missing element in a shuffled array using bitwise XOR. Time Complexity: $O(n)$, Space Complexity: $O(1)$.
- [Array Find Missing Element (Brute Force Solution)](ArrayFindTheMissingElementBruteForceSol.py): Finds a missing element by sorting both arrays and comparing them. Time Complexity: $O(n \log n)$.
- [Array Find Missing Element (Hash Table Solution)](ArrayFindTheMissingElementHashTableSol.py): Finds a missing element using a hash table (dictionary) to track element counts. Time Complexity: $O(n)$.
- [Array Find Missing Element (Sum/Subtract Solution)](ArrayFindTheMissingElementSumSol.py): Finds a missing element by calculating the difference between the sums of the two arrays. Time Complexity: $O(n)$.
- [Array Pair Sum Solution](ArrayPairSumSol.py): Finds all unique pairs in an array that sum up to a specific value $k$ using a set. Time Complexity: $O(n)$.
File renamed without changes.
2 changes: 1 addition & 1 deletion deque/README.md → Deque/README.md
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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`, and `removeRear`. Time Complexity: $O(1)$ for front operations, $O(n)$ for rear operations (due to list shifting).
File renamed without changes.
4 changes: 2 additions & 2 deletions Error-debug/README.md → ErrorHandling/README.md
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@@ -1,7 +1,7 @@
# Error and Debugging
# Error and Handling

This directory contains examples of error handling and debugging techniques in Python.

## Contents

- [Error and Exceptions](ErrorExceptions.py): Demonstrates the use of `try`, `except`, `else`, and `finally` blocks for robust error handling, specifically validating integer user input.
- [Error and Exceptions](ErrorExceptions.py): Demonstrates the use of `try`, `except`, `else`, and `finally` blocks for robust error handling.
10 changes: 5 additions & 5 deletions LinkedLists/README.md
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Expand Up @@ -4,8 +4,8 @@ This directory contains Python implementations of various types of linked lists

## 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 node and basic linkage. Time Complexity: $O(1)$ for linkage.
- [Doubly Linked List Implementation](DoublyLinkedListImple.py): Basic implementation of a doubly linked list node with `prev` and `next` pointers. Time Complexity: $O(1)$ for linkage.
- [Singly Linked List Cycle Check](SinglyLinkedListCycleCheckImple.py): Implements Floyd's Cycle-Finding Algorithm (two pointers) to detect cycles in a linked list. Time Complexity: $O(n)$.
- [Linked List Reversal](LinkedListReversal.py): Reverses a singly linked list in-place. Time Complexity: $O(n)$.
- [Nth to Last Node](LinkedListNthToLastNode.py): Finds the $n$-th to last node in a singly linked list using two pointers. Time Complexity: $O(n)$.
28 changes: 12 additions & 16 deletions LinkedLists/SinglyLinkedListCycleCheckImple.py
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -31,6 +31,7 @@ def cycle_check(node):
if pt2 == pt1:
return True
return False

# Test
# Create a Linked List
a = LinkedListNode(1)
Expand All @@ -39,19 +40,14 @@ def cycle_check(node):
# Create a cycle
a.nextnode = b
b.nextnode = c
# This is a cycle -- to test non-cycle scnerio comment this line
c.nextnode = a

print (a.value)
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())
print(f"Node A value: {a.value}")
print(f"Node B value: {b.value}")
print(f"Node C value: {c.value}")

print(f"Cycle detected (should be True): {a.cycle_check()}")

# Breaking the cycle for testing
c.nextnode = None
print(f"Cycle detected after breaking (should be False): {a.cycle_check()}")
59 changes: 30 additions & 29 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -35,23 +35,23 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for more details.

## 📖 Table of Contents

- [Getting Started](#getting-started)
- [Project Structure](#project-structure)
- [Data Structures](#data-structures)
- [Arrays](#arrays)
- [Linked Lists](#linked-lists)
- [Stacks](#stacks)
- [Queues](#queues)
- [Deque](#deque)
- [Trees](#trees)
- [Algorithms](#algorithms)
- [Sorting](#sorting)
- [Recursion & Dynamic Programming](#recursion--dynamic-programming)
- [Graph Algorithms](#graph-algorithms)
- [Error Handling & Debugging](#error-handling--debugging)
- [Usage](#usage)
- [Quick Reference](#quick-reference)
- [License](#license)
- [🚀 Getting Started](#getting-started)
- [📁 Project Structure](#project-structure)
- [📊 Data Structures](#data-structures)
- [Arrays 🔤](#arrays)
- [Linked Lists 🔗](#linked-lists)
- [Stacks 📚](#stacks)
- [Queues 📦](#queues)
- [Deque 🔄](#deque)
- [Trees 🌳](#trees)
- [Algorithms](#algorithms)
- [Sorting 📊](#sorting)
- [Recursion & Dynamic Programming 🔀](#recursion--dynamic-programming)
- [Graph Algorithms 🗺️](#graph-algorithms)
- [⚠️ Error Handling & Debugging](#error-handling--debugging)
- [📖 Usage](#usage)
- [📊 Quick Reference](#quick-reference)
- [📄 License](#license)

---

Expand All @@ -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
Expand All @@ -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
Expand All @@ -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.
Expand All @@ -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.
Expand All @@ -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)

---

Expand All @@ -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) - $O(n^2)$ worst case
- [Merge Sort](Sorting/MergeSortImple.py) - $O(n \log n)$
- [Quick Sort](Sorting/QuickSortImple.py) - $O(n \log n)$ average

Expand All @@ -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.

---

Expand Down Expand Up @@ -214,8 +214,9 @@ New to DSA? Follow this recommended order:

## 🔮 Roadmap

- [x] Correct naming conventions (PascalCase)
- [x] Include complexity analysis for each solution
- [ ] Add more graph algorithms (Dijkstra, Bellman-Ford)
- [ ] Include complexity analysis for each solution
- [ ] Add interactive examples/visualizations
- [ ] Create a difficulty level classification
- [ ] Add more test cases
Expand Down
11 changes: 5 additions & 6 deletions Recursion/FibonacciSeqDynamic.py
Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,11 @@
# memoization + recursion = dynamic programming
# Author: Pradeep K. Pant, ppant@cpan.org

# Instantiate Cache information
n = 10
cache = [None] * (n + 1)

# Implement fibonacci_dynamic
def fibonacci_dynamic(n):
def fibonacci_dynamic(n, cache=None):
if cache is None:
cache = [None] * (n + 1)

# Base Case
if n == 0 or n == 1:
return n
Expand All @@ -17,7 +16,7 @@ def fibonacci_dynamic(n):
return cache[n]

# Recursive call to and keep setting cache
cache[n] = fibonacci_dynamic(n - 1) + fibonacci_dynamic(n - 2)
cache[n] = fibonacci_dynamic(n - 1, cache) + fibonacci_dynamic(n - 2, cache)
return cache[n]

# Test
Expand Down
12 changes: 6 additions & 6 deletions Sorting/README.md
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,9 @@ 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.
- [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.
- [Bubble Sort](BubbleSortImple.py): Implementation of Bubble Sort. Time Complexity: $O(n^2)$.
- [Selection Sort](SelectionSortImple.py): Implementation of Selection Sort, making only one exchange per pass. Time Complexity: $O(n^2)$.
- [Insertion Sort](InsertionSortImple.py): Implementation of Insertion Sort, maintaining a sorted sublist. Time Complexity: $O(n^2)$.
- [Shell Sort](ShellSortImple.py): Implementation of Shell Sort (diminishing increment sort). Time Complexity: $O(n^2)$ worst case.
- [Merge Sort](MergeSortImple.py): A recursive "divide and conquer" algorithm. Time Complexity: $O(n \log n)$.
- [Quick Sort](QuickSortImple.py): Implementation of Quick Sort (partition exchange sort). Time Complexity: $O(n \log n)$ average.
4 changes: 2 additions & 2 deletions Stacks/README.md
Original file line number Diff line number Diff line change
Expand Up @@ -4,5 +4,5 @@ This directory contains Python implementations of the Stack data structure and i

## 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 LIFO (Last-In-First-Out) stack using a Python list. Time Complexity: $O(1)$ for push/pop/peek.
- [Balanced Parentheses Check](BalanceParenthesesCheckImple.py): Uses a stack to check if a string of opening and closing parentheses (round, square, and curly) is balanced. Time Complexity: $O(n)$.
File renamed without changes.
18 changes: 9 additions & 9 deletions Trees/README.md
Original file line number Diff line number Diff line change
Expand Up @@ -5,19 +5,19 @@ This directory contains Python implementations of various tree-based data struct
## Contents

### Binary Search Trees (BST)
- [Binary Search Tree Implementation](BinarySearchTreesImple.py): A comprehensive implementation of a BST with `TreeNode` and `BinarySearchTree` classes, including insertion, deletion, and search.
- [Validate BST (Solution 1)](BinarySearchTreeCheckImpleSol1.py): Validates a BST by performing an in-order traversal and checking if the resulting values are sorted.
- [Validate BST (Solution 2)](BinarySearchTreeCheckImpleSol2.py): Validates a BST by keeping track of the minimum and maximum allowable values for each node.
- [Trim a BST](TrimBinarySearchTreeImple.py): Trims a BST so that all node values fall within a specified range $[min, max]$.
- [Binary Search Tree Implementation](BinarySearchTreesImple.py): A comprehensive implementation of a BST with `TreeNode` and `BinarySearchTree` classes. Time Complexity: $O(\log n)$ average, $O(n)$ worst case.
- [Validate BST (Solution 1)](BinarySearchTreeCheckImpleSol1.py): Validates a BST by performing an in-order traversal. Time Complexity: $O(n)$.
- [Validate BST (Solution 2)](BinarySearchTreeCheckImpleSol2.py): Validates a BST by keeping track of the minimum and maximum allowable values. Time Complexity: $O(n)$.
- [Trim a BST](TrimBinarySearchTreeImple.py): Trims a BST so that all node values fall within a specified range $[min, max]$. Time Complexity: $O(n)$.

### Search Algorithms
- [Binary Search (Iterative)](BinarySearchImple.py): Iterative implementation of the binary search algorithm on a sorted list.
- [Binary Search (Recursive)](BinarySearchRecursiveImple.py): Recursive implementation of the binary search algorithm.
- [Binary Search (Iterative)](BinarySearchImple.py): Iterative implementation of the binary search algorithm. Time Complexity: $O(\log n)$.
- [Binary Search (Recursive)](BinarySearchRecursiveImple.py): Recursive implementation of the binary search algorithm. Time Complexity: $O(\log n)$.

### Heaps
- [Binary Heap Implementation](BinaryHeapImple.py): Implements a min-heap using a recursive approach, including `insert`, `delMin`, and `buildHeap`.
- [Binary Heap Implementation](BinaryHeapImple.py): Implements a min-heap using a recursive approach. Time Complexity: $O(\log n)$ for insert/delete, $O(n)$ for buildHeap.

### Tree Representations & Traversals
- [Nodes and References Representation](TreeRepresentationWithNodesReferences.py): A simple implementation of a binary tree using a class-based nodes and references approach.
- [List of Lists Representation](buildTreeTest.py): Demonstrates building and manipulating a tree using a "list of lists" approach.
- [Tree Level Order Print](TreeLevelOrderPrintImple.py): Prints a binary tree in level order (breadth-first) using a queue, with each level on a new line.
- [List of Lists Representation](BuildTreeTest.py): Demonstrates building and manipulating a tree using a "list of lists" approach.
- [Tree Level Order Print](TreeLevelOrderPrintImple.py): Prints a binary tree in level order (breadth-first) using a queue. Time Complexity: $O(n)$.