jonathanagustin

"""
https://leetcode.com/problems/top-k-frequent-words/

Given a non-empty list of words, return the k most frequent elements.

Your answer should be sorted by frequency from highest to lowest. 
If two words have the same frequency, then the word with the 
lower alphabetical order comes first.

collections.Counter([iterable-or-mapping]) counts hashable objects

jonathanagustin

"""
https://py.checkio.org/forum/post/9298/sorted-function-explanation-please/

This will sort a list of tuples by strings (second tuple item) 
and then by number in reversed order when strings are equal.
"""

list_of_tuples = [(1, 'a'), (1, 'b'), (2, 'a'), (2, 'b')]
list_of_tuples.sort(key=lambda t:(t[1], -t[0]))
print(list_of_tuples) 

jonathanagustin

# Parallel sorting of lists

data = zip(list1, list2)
data.sort()
list1, list2 = map(lambda t: list(t), zip(*data))

jonathanagustin

"""
https://practice.geeksforgeeks.org/problems/inorder-traversal/1
"""
def InOrder(root):
  
    if root is None:
        return
    
    InOrder(root.left)
    

jonathanagustin

Docker

Lessons Learned

/root/compile: line 2: $'\r': command not found

The above means you need to dos2unix the file.

Useful commands

jonathanagustin

"""
https://practice.geeksforgeeks.org/problems/height-of-binary-tree/1

- use recursion to find the height
- use max on left and right branch on every recursion (add 1 every iteration)
"""
def height(root):
    if root is None:
        return 0
    return 1 + max(height(root.left), height(root.right))

jonathanagustin

"""
https://practice.geeksforgeeks.org/problems/finding-middle-element-in-a-linked-list/1

- Use "tortoise and the hare" method to find the middle
- Use a pointer that increments half the "speed" of another pointer
"""
def findMid(head):
    
    if head is None:
        return None

jonathanagustin

"""
https://www.algoexpert.io/questions/Branch%20Sums
"""

class BinaryTree:
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None

jonathanagustin

"""
https://www.algoexpert.io/questions/Find%20Closest%20Value%20In%20BST

Average: Theta(logn) time | Theta(logn) space 
Worst: O(n) time | O(n) space

This solution takes up O(n) space because of recursion.

float('inf') is used to set a unbounded upper value for comparison
"""

jonathanagustin

"""
https://www.algoexpert.io/questions/Two%20Number%20Sum

O(nlogn) time | O(1) space
This algorithm sorts the arrays and then puts two index 
pointers at the edges and then advances towards the 
middle to find a solution.
"""
def twoNumberSum(array, targetSum):
	# sort array (really a list) first