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14 changes: 7 additions & 7 deletions Arrays/README.md
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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: $O(n)$.
- [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: $O(n)$.
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7 changes: 7 additions & 0 deletions Deque/README.md
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@@ -0,0 +1,7 @@
# Deque

This directory contains a Python implementation of a Double-ended queue (Deque).

## Contents

- [Deque Implementation](DequeImple.py): Implementation of a Deque using a Python list. Operations at both ends: `addFront`, `addRear`, `removeFront`, `removeRear`. Time Complexity: $O(1)$ for front operations, $O(n)$ for rear operations (due to list shifting).
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6 changes: 3 additions & 3 deletions Error-debug/README.md → ErrorHandling/README.md
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@@ -1,7 +1,7 @@
# Error and Debugging
# Error Handling

This directory contains examples of error handling and debugging techniques in Python.
This directory contains examples of error handling and debugging 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.
14 changes: 7 additions & 7 deletions GraphAlgorithms/README.md
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@@ -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 graph-based algorithms and data structures.

## 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 a Graph Abstract Data Type using an adjacency list.
- [Breadth First Search (BFS)](BFS.py): Implementation of BFS, demonstrated with the Word Ladder problem. Time Complexity: $O(V + E)$.
- [Depth First Search (DFS) General](DFSGeneral.py): General implementation of Depth First Search. Time Complexity: $O(V + E)$.
- [Knight's Tour Problem (Graph Generation)](TheKnightsTourProblem.py): Building a graph to represent the Knight's Tour problem.
- [Knight's Tour Problem (DFS Solution)](DFSImpleTheKnightsTourProblem.py): Solving the Knight's Tour problem using DFS.
- [Word Ladder Problem](WordLadderProblem.py): Implementation of the Word Ladder problem using graphs.
12 changes: 6 additions & 6 deletions LinkedLists/README.md
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@@ -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 singly and doubly linked lists 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.
- [Doubly Linked List Implementation](DoublyLinkedListImple.py): Basic implementation of a doubly linked list.
- [Singly Linked List Cycle Check](SinglyLinkedListCycleCheckImple.py): Implementation of Floyd's cycle-finding algorithm to detect cycles in a linked list. Time Complexity: $O(n)$.
- [Linked List Reversal](LinkedListReversal.py): In-place reversal of a singly linked list. Time Complexity: $O(n)$.
- [Linked List N-th to Last Node](LinkedListNthToLastNode.py): Finding the $n$-th node from the end of a singly linked list. Time Complexity: $O(n)$.
17 changes: 5 additions & 12 deletions LinkedLists/SinglyLinkedListCycleCheckImple.py
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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 current node
pt1 = self
pt2 = self
# loop through end of the list
while pt2 != None and pt2.nextnode != None:
pt1 = pt1.nextnode
Expand All @@ -46,12 +46,5 @@ 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.

# Now cycle_check is a proper instance method.
print(a.cycle_check())


6 changes: 3 additions & 3 deletions Queues/README.md
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@@ -1,8 +1,8 @@
# Queues

This directory contains Python implementations of the Queue data structure.
This directory contains Python implementations of Queue data structures.

## 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): Implementation of a FIFO (First-In-First-Out) queue using a Python list. Time Complexity: $O(n)$ for enqueue, $O(1)$ for dequeue.
- [Queue with Two Stacks](QueueWith2StacksImple.py): Implementation of a queue using two stacks. Time Complexity: $O(1)$ amortized for both enqueue and dequeue.
22 changes: 11 additions & 11 deletions README.md
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Expand Up @@ -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) - $O(n^2)$
- [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
11 changes: 5 additions & 6 deletions Recursion/FibonacciSeqDynamic.py
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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
27 changes: 11 additions & 16 deletions Recursion/README.md
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@@ -1,21 +1,16 @@
# Recursion

This directory contains Python implementations of problems solved using recursion and dynamic programming.
This directory contains Python implementations of recursive algorithms and dynamic programming problems.

## 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.
- [Fibonacci Sequence (Dynamic Programming)](FibonacciSeqDynamic.py): Fibonacci implementation using memoization. Time Complexity: $O(n)$.
- [Fibonacci Sequence (Iterative)](FibonacciSeqIterative.py): Iterative implementation of Fibonacci. Time Complexity: $O(n)$.
- [Fibonacci Sequence (Recursive)](FibonacciSeqRecursion.py): Simple recursive implementation of Fibonacci. Time Complexity: $O(2^n)$.
- [Coin Change Problem (Dynamic Programming)](CoinChangeProblemDynamic.py): Solving the coin change problem using DP. Time Complexity: $O(n \cdot m)$.
- [Coin Change Problem (Recursive)](CoinChangeProblemRecursion.py): Recursive approach to the coin change problem.
- [Recursion Cumulative Sum](RecursionCumulativeSum.py): Calculating the cumulative sum of numbers up to $n$ using recursion. Time Complexity: $O(n)$.
- [Recursion Reverse String](RecursionReverseStr.py): Reversing a string using recursion. Time Complexity: $O(n)$.
- [Recursion String Permutation](RecursionStrPermutation.py): Generating all permutations of a string. Time Complexity: $O(n!)$.
- [Recursion Sum of Digits](RecursionSumOfDigits.py): Calculating the sum of digits of a number using recursion. Time Complexity: $O(\log_{10} n)$.
- [Recursion Word Split](RecursionWordSplit.py): Dynamic programming solution to split a string into words based on a dictionary.
12 changes: 6 additions & 6 deletions Sorting/README.md
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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, improving on Bubble Sort by 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), improving on Insertion 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), using divide and conquer in-place. Time Complexity: $O(n \log n)$ average.
6 changes: 3 additions & 3 deletions Stacks/README.md
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@@ -1,8 +1,8 @@
# Stacks

This directory contains Python implementations of the Stack data structure and its applications.
This directory contains Python implementations of Stack data structures and their applications.

## 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 LIFO (Last-In-First-Out) stack implementation.
- [Balanced Parentheses Check](BalanceParenthesesCheckImple.py): Algorithm to check for balanced parentheses in a string using a stack. Time Complexity: $O(n)$.
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