Coding Interview Tips

Generate a list of 0,1 as binary representation. It's great if you have any challeges that can use bit manipulations. For example return all permutations of a list.

def createBin(size):
  num = 2**size - 1
  binned = bin(num)
  res = [int(d) for d in str(binned)[2:]]
  return res

create linked list from an array, transform linked list to an array:

def buildList(arr):
    fake_head = ListNode()
    prev = fake_head
    for item in arr:
        next_val = ListNode(item)
        prev.next = next_val
        prev = next_val
    return fake_head.next

def getArrFromList(head):
    arr = []
    cur = head
    while cur:
        arr.append(cur.val)
        cur = cur.next
    return arr

heap with custom comparator:

class Node(object):
    def __init__(self, count, val):
        self.count = count
        self.val = val

    def __lt__(self, other):
        return self.count < other.count

    # just a nice print
    def __repr__(self):
        return f'{self.val}: {self.count}'

nodes = [Node(1,1), Node(2,2)]
heapify(nodes)

Create a matrix with width*height:

matrix = [[0 for x in range(w)] for y in range(h)]