chiphuyen / coding-exercises

My implementation of useful data structures, algorithms, as well as my solutions to programming puzzles.

514 201 Language: Python Updated: 1mo ago

coding-challenge coding-exercises coding-interviews training-materials

README

This repository contains my implementation of useful data structures, algorithms,
games, as well as my solutions to programming puzzles.

Each item is marked with a difficulty level.
1 - easy
2 - medium
3 - hard

If a file name starts with 'lc', it's a problem from leetcode.com

Written in python3. Thanks Danijar Hafner (@danijar) for the inspiration.

Data structures

Linked lists

[x] List class (linked_list.py) - 1
[ ] Remove duplicates (linked_list_algos.py)
[ ] Find nth last element (linked_list_algos.py)
[ ] Remove node given only its object (linked_list_algos.py)
[ ] Sum linked lists with one digit per node (linked_list_algos.py)
[ ] Find beginning of circle (linked_list_algos.py)

Trees

[x] Binary heap class (binary_heap.py) - 2
[ ] Binary tree class (binary_tree.py) - 1
[x] Binary search tree class that allows duplicate values (binary_search_tree.py) - 2
```
BST class inherits binary tree class
```
[ ] Red black tree class (red_black_tree.py)
[ ] B+ tree class (b_tree.py) - 3
[x] Trie class that allows word removal (trie.py) - 2
[x] Check if a binary tree is a binary search tree (binary_tree_algos.py) - 2
[ ] Check if a binary tree is balanced (binary_tree_algos.py)
[ ] Find first common ancestor of two nodes in a binary tree (binary_tree_algos.py)
[ ] Get all nodes of depth n in a binary tree (binary_tree_algos.py)
[ ] Given two large trees, check if the first is a subtree of the second (binary_tree_algos.py)
[ ] Find all sub paths in a binary tree that sum up to x (binary_tree_algos.py)
[ ] Create a balanced binary search tree from a sorted array (bst_algos.py)

Graphs

[ ] Undirected graph class
[ ] Directed graph class
[ ] Breadth first search (search.py)
[ ] Depth first search (search.py)
[ ] A-star (search.py)

Stacks and queues

[ ] Queue class (queue.py)
[x] Heap priority queue (priority_queue.py) - 1
[ ] Stack class (stack.py)
[ ] Stack that finds min in O(1) (min_stack.py)
[ ] Solve Hanoi towers using stacks (stack_algos.py)
[ ] Sort stack using only push, pop, peek and empty (stack_algos.py)
[ ] Build a queue using two stacks (stack_algos.py)

Algorithms

Sorting

[x] Insertion sort (sort.py) - 1
[x] Selection sort (sort.py) - 1
[x] Merge sort (sort.py) - 2
[x] Heap sort (sort.py) - 2
[x] Quick sort (sort.py) - 2
[x] Counting sort (sort.py) - 2
[x] Radix sort (sort.py) - 2
[x] Bucket sort (sort.py) - 2

Dynamic Programming

[ ] Computing a Fibonacci sequence
[ ] Find the longest common subsequence between two strings

Recursion

[ ] Find all permutations of a string
[ ] Find all subsets of a set
[ ] Find all proper combinations of n parentheses
[ ] Bucket fill
[ ] Check if it's possible to make a change with a set of coins
[ ] Check if it's possible to weight two objects with a set of weights
[ ] Eight queen

Programming Puzzles

String Manipulation

[x] Check if two strings are anagrams in O(n + m) time (anagrams.py) - 1
[x] Find the longest palindromic substring in O(n^2) time (lc_longest_palindrome.py) - 2
[x] Check if a string has balanced delimiters in O(n) time (delim_balanced.py) - 2
[x] Reverse words while maintaining spaces and tabs in O(n) time (reverse_words.py) - 2
[x] Longest substring without repeating characters in O(n) time (lc_longest_nonrepeat_substring.py) - 2
[x] Longest contiguous substring of 2 distinct characters in O(n) time (substring_two_chars.py) - 2
[ ] Remove duplicate chars in a string
[ ] Encode and decode Caesar cipher (caesar.py)
[ ] Check if a string is a rotation of another

Mathematical

[x] Reverse integers (lc_reverse_int.py) - 1
[x] Sieve of Eratosthenes (sieve_prime.py) - 1

[x] Two sum in O(n) time (lc_two_sum.py) - 1

Given an array of integers, return indices of the two numbers 
such that they add up to a specific target.

[x] Year with maximum population (year_max_pop.py) - 1

Given a list of people with their years of birth and death, 
find the year with max population

[x] FizzBuzz (fizzbuzz.py) - 1
[x] ZigZag conversion (lc_zigzag_convert.py) - 2
[x] Find sum of all subarrays of an array (subarray_sum.py) - 2
[x] Add two numbers, each represented by a reverse linked list (lc_add_number_reverse.py) - 2
[x] Find the median of two sorted arrays in O(log(m+n)) time (lc_median_arrays.py) - 3
[ ] Find nth smallest number that can be created using a list of prime factors
[ ] Count occurences of given digit in all numbers up to n
[ ] Rotate N x N matrix in place

Games

[x] Game of ghost (ghost.py) - 3

Ghost is a word game in which players take turns adding letters to a
growing word fragment, trying not to be the one to complete a valid word.

This implementation uses minimax with alpha-beta pruning to make sure the computer always wins.
It uses a Trie to keep track of the dictionary.

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