Data structure

Tree insert function

def insert(root, val):
	if not root: 
		return TreeNode(val) // create a node

	if val > root.val:
		root.right = insert(root.right, val)
	elif val < root.val:
		root.left = insert(root.left, val)
	return root

BST - remove

def minValueNode(root

Recursion

writing functions that call themselves with smaller subproblems

depth first search (DFS)

traversing trees by exploring as deep as possible before backtracking

breadth first search

traversing trees level by level using a queue

deque()

1. double-ended queue

how to add / remove elements in deque

q = deque()
q.append(5) # [5]
q.append(10) # [5, 10]
q.appendleft(1) # [1, 5,10]

q.popleft() # remove from left [5,10]
q.pop() # remove from right [5]