Leetcode

This is my solution to Leetcode Online Judge's problems. Currently I am revamping the problems all over again towards more idiomatic Python. Stay tuned for updates.

Feel free to submit pull requests for submitting more elegant solution.

###List of idiomatic Python I prefer (as of now)

Prefer list comprehension over map / filter.

	# from Gray Code

	# Bad
	def grayCode(self, n):
        return map(lambda x: (x / 2) ^ x, range(1 << n))

	# Idiomatic
	def grayCode(self, n):
        return [(x / 2) ^ x for x in range(1 << n)]

Prefer using in keyword over repetitive variable in conditional statement.

	# from Post Order Traversal

	# Bad
	if parent.right == None or parent.right == prev

	# Idiomatic
	if parent.right in (None, prev):

Prefer using docstring over single line comment when describing functionality of a method.

	# from Search Insert Position

	# Bad
	# Iterative solution is also fine.
	def searchInsert(self, A, target):

	# Idiomatic
	def searchInsert(self, A, target):
    	"""Iterative solution is also fine.
    	"""

Prefer implicit evaluation of condition (e.g. if, while, etc.) over explicit comparison in condition.
Notice empty list and dictionary will be evaluated to False, so that is very handy.

	# from Binary Tree Preorder Traversal

	# Bad
	while len(stack) > 0:
		current = stack.pop()

	# Idiomatic
	while stack:
		current = stack.pop()

Prefer is None over == None. Notice is looks for referential equality, and None is a singleton.
The fundamental reason for this preference is much improved speed, and == can be overriden by __eq__.

	# from Binary Tree Preorder Traversal

	# Bad
	if root == None:

	# Idiomatic
	if root is None:

One interesting side note in Python regarding this is on

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saxon17/Leetcode-1

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