Algorithms

Classic CS algorithms in C++ and Python, organized by category with a CMake build system.

Structure

algorithms/
├── graph/           Dijkstra, Kruskal MST, Prim MST
├── sorting/         Selection, Insertion, Merge, Heap, Counting, Bucket sort + median finder
├── math/            Gaussian elimination (fractions), Gray code, Hex ↔ decimal converter
├── strings/         Reverse Polish Notation evaluator, Substring search
└── python/          Dijkstra (Jupyter Notebook)

Build (C++)

Requires CMake ≥ 3.16 and a C++17 compiler (GCC, Clang, or MSVC).

cmake -B build
cmake --build build

Each algorithm compiles to its own named executable inside build/.

Algorithms

Graph

File	Algorithm	Complexity
graph/dijkstra.cpp	Dijkstra's shortest path	O(V²)
graph/kruskal.cpp	Kruskal's MST (union-find)	O(E log E)
graph/prim.cpp	Prim's MST	Work-in-progress

Sorting

File	Algorithm	Complexity
sorting/selection_sort.cpp	Selection sort	O(n²)
sorting/insertion_sort.cpp	Insertion sort	O(n²)
sorting/merge_sort.cpp	Merge sort	O(n log n)
sorting/heap_sort.cpp	Heap sort	O(n log n)
sorting/counting_sort.cpp	Counting sort	O(n + k)
sorting/bucket_sort.cpp	Bucket sort	O(n + k)
sorting/selection_sort_median.cpp	Selection sort + median	O(n²)

Math

File	Algorithm
math/gaussian_elimination/	Row-reduction with exact fractions
math/gray_code.cpp	N-bit Gray code generator
math/hex_converter.cpp	Hex ↔ decimal bidirectional converter

Strings

File	Algorithm
strings/rpn_evaluator.cpp	Reverse Polish Notation evaluator
strings/substring_search.cpp	Substring occurrence counter

Python

File	Algorithm
python/dijkstra.ipynb	Dijkstra's shortest path (graph class)

Bug fixes applied

File	Bug	Fix
strings/rpn_evaluator.cpp	Use-after-free in custom stack; wrong -// operand order	Replaced with std::stack; fixed pop order
graph/dijkstra.cpp	Out-of-bounds array walk; infinity=1000 too small	Safe min-search; INT_MAX sentinel
sorting/heap_sort.cpp	heap_sort() body was empty	Implemented extract-max loop
sorting/bucket_sort.cpp	Wrong distribution index	Fixed to buckets[value][count++]
sorting/selection_sort.cpp	Missing braces put counter++ outside inner loop	Added braces
sorting/counting_sort.cpp	tmp array never freed	Added delete[] tmp
strings/substring_search.cpp	printf("%x") printed count as hex	Changed to %d
python/dijkstra.ipynb	return ValueError(...) instead of raising	Changed to raise
math/gaussian_elimination/main.cpp	#include "matrix.cpp" (non-standard)	Changed to #include "matrix.h"