Documenting practices on various coding platforms such as LeetCode, Kattis, HackerRank, etc. Additionally, adding code snippets to show how to implement certain data structures and algorithms (DSA) from scratch.
Sorting
| Category | Algorithm | Description | Implementation Link |
|---|---|---|---|
| Comparison-based | Bubble Sort | Simple comparison-based sorting | Bubble Sort |
| Comparison-based | Insertion Sort | Builds the final sorted array one item at a time | Insertion Sort |
| Comparison-based | Selection Sort | Selects the smallest element from an unsorted list in each iteration and places that element at the beginning | Selection Sort |
| Comparison-based | Merge Sort | Divides the array into halves, sorts them and merges them back together | Merge Sort |
| Comparison-based | Quick Sort | Divides the array into partitions and sorts them recursively | Quick Sort |
| Comparison-based | Random Quick Sort | Uses a random pivot to divide the array into partitions and sorts them recursively | Random Quick Sort |
| Non-comparison-based | Bucket Sort | Distributes elements into buckets and sorts each bucket individually | Bucket Sort |
| Non-comparison-based | Counting Sort | Counts the number of objects having distinct key values and uses arithmetic to determine the positions of each key | Counting Sort |
| Non-comparison-based | Radix Sort | Sorts numbers by processing individual digits | Radix Sort |
Arrays
Stack and Queue
HashMap / Hash Table
Direct Addressing Table (simplified hash table)
Graph
Single-Source Shortest Path: Bellman Ford
Single-Source Shortest Path: Dijkstra
Single-Source Shortest Path: BFS on unweighted graph
Single-Source Shortest Path: Modified Dijkstra
Kadane's Algorithm
Sliding Window
Prefix Sum
Two Pointers
Gradually adding the questions in different languages (Python, Julia & C++)
Arrays & Hashing
| Question | Description | Difficulty | Type | Solution |
|---|---|---|---|---|
| 1. Two Sum | Find two indices in a vector such that the numbers add up to a target value |
Easy | Arrays, Hashing |   |
| 242. IsAnagram | Determine if two strings are anagrams of each other |
Easy | Hashing | |
| 217. Contains Duplicate | Check if a vector contains any duplicates |
Easy | Arrays, Hashing | |
| 36. Valid Sudoku | Determine if a 9x9 Sudoku board is valid |
Medium | Arrays, Hashing | |
| 128. Longest Consecutive Sequence | Find the length of the longest consecutive elements sequence |
Medium | Arrays, Hashing | |
| 271. Encode and Decode Strings | Encode a list of strings to a single string and decode it back to the list |
Medium | Arrays, String Manipulation | |
| 49. Group Anagrams | Group strings into anagrams |
Medium | Hashing, Sorting | |
| 219. Close Duplicates | Check if a vector contains duplicates within a given range |
Easy | Sliding Window | |
| 1343. NumOfSubarrays | Count subarrays with average greater than or equal to a threshold |
Medium | Sliding Window | |
| 1929. Concatenation of Array | Return array ans of length 2n where ans[i] == nums[i] and ans[i + n] == nums[i] |
Easy | Arrays | |
Two Pointers
| Question | Description | Difficulty | Type | Solution |
|---|---|---|---|---|
| 125. Valid Palindrome | Determine if a string is a palindrome, considering only alphanumeric characters and ignoring cases | Easy | Two Pointers | |
| 15. Three Sum | Find all unique triplets in the array which gives the sum of zero | Medium | Two Pointers | |
| 11. Container With Most Water | Find two lines that together with the x-axis form a container, such that the container contains the most water | Medium | Two Pointers | |
| Two Sum Part 2 | Find two indices in a sorted array such that they add up to a specific target | Medium | Sliding Window | |
| Trapping Rain Water | Calculate how much water can be trapped after raining | Hard | Sliding Window | |
Stack
| Question | Description | Difficulty | Type | Solution |
|---|---|---|---|---|
| 20. Valid Parenthesis | Determine if the input string has valid parentheses | Easy | Stack | |
Sliding Window
| Question | Description | Difficulty | Type | Solution |
|---|---|---|---|---|
| 121. Best Time to Buy and Sell Stock | Find the maximum profit you can achieve from one transaction | Easy | Sliding Window | |
| 3. Longest Substring Without Repeating Characters | Find the length of the longest substring without repeating characters | Medium | Sliding Window | |
| 424. Longest Repeating Character Replacement | Find the length of the longest substring containing the same letter you can get after performing k replacements | Medium | Sliding Window | |
| 76. Minimum Window Substring | Find the minimum window substring of s such that every character in t is included |
Hard | Sliding Window | |
Linked List
| Question | Description | Difficulty | Type | Solution |
|---|---|---|---|---|
| 21. Merge Two Sorted Lists | Merge two sorted linked lists and return it as a new sorted list | Easy | Linked List | |
Kattis Problems
| Problem ID | Description | Difficulty | Type | Solution |
|---|---|---|---|---|
| hip hip | Print "Hipp hipp hurra!" 20 times | Easy | Easy Coding Challenges | |
| storafmaeli | Check if it's anniversary | Easy | Easy Coding Challenges | |
| fyrirtækjanafn | Filter out consonants from input | Easy | Easy Coding Challenges | |
| peningar | Calculate values accumulated from circular cells | Easy | Easy Coding Challenges | |
| framvindustika | Print progress bar and % | Medium | Easy Coding Challenges | |
| message | Extract letters from nested list to form a message | Easy | Easy Coding Challenges | |
| bidendalausbid | Calculate waited time in minutes | Easy | Easy Coding Challenges | |
| hlaupafmaeli | Check birthday for leap year | Medium | Easy Coding Challenges | |
| lidaskipting2 | Find min and max number of competitive teams that can be formed | Easy | Easy Coding Challenges | |
| fleytitala | Find min and max number of competitive teams that can be formed | Medium | Easy Coding Challenges | |
| subaruba | Ubbi dubbi game | Medium | Array | |
| gangur | Count passing pairs of people | Easy | Array | |
| taktsvedjur | Calculate scores with multipliers | Easy | Array | |