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Python solution for Leetcode. Moved tohttps://github.com/jw2013/Leetcode-Py
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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.
- Prefer list comprehension over map / filter.
# from Gray Code# Baddef grayCode(self, n): return map(lambda x: (x / 2) ^ x, range(1 << n))# Idiomaticdef grayCode(self, n): return [(x / 2) ^ x for x in range(1 << n)]- Prefer using
inkeyword over repetitive variable in conditional statement.
# from Post Order Traversal# Badif parent.right == None or parent.right == prev# Idiomaticif 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):# Idiomaticdef 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# Badwhile len(stack) > 0:current = stack.pop()# Idiomaticwhile stack:current = stack.pop()- Prefer
is Noneover== None. Noticeislooks for referential equality, andNoneis a singleton.
The fundamental reason for this preference is much improved speed, and==can be overriden by__eq__.
# from Binary Tree Preorder Traversal# Badif root == None:# Idiomaticif root is None:One interesting side note in Python regarding this is onStackoverflow. Trust me, that is worth your 60 seconds of time. But that only works in REPL though, not on a executable python file.
READ THIS or above two rules will only do you harm:
Sometimes you have to useif foo is not None overif foo. For example, if foo is 0, thenif foo will become False. But 0 is not None. Just watch out. A rule of the thumb is if you want to check if the default argument of a function is None, then useif foo is not None, otherwise you can most likely useif foo if you know what you are doing.
- Consider using enumerate when index accessing looks verbose
# from Two Sum# Badfor i in range(len(nums)): if target - nums[i] in lookup: return (lookup[target - nums[i]] + 1, i + 1) lookup[nums[i]] = i # Idiomatic for i, num in enumerate(nums): if target - num in lookup: return (lookup[target - num] + 1, i + 1) lookup[num] = i- Readability counts.
"Any fool can write code that a computer can understand. Good programmers write code that humans can understand." Martin Fowler is right.
# from Edit Distance# Baddef minDistance(self, word1, word2): distance = [[i] for i in range(len(word1) + 1)] distance[0] = [i for i in range(len(word2) + 1)] for i in range(1, len(word1) + 1): for j in range(1, len(word2) + 1): distance[i].append(min(distance[i - 1][j] + 1, distance[i][j - 1] + 1, distance[i - 1][j - 1] + (word1[i - 1] != word2[j - 1]))) return distance[-1][-1] # Idiomatic def minDistance(self, word1, word2): distance = [[i] for i in range(len(word1) + 1)] distance[0] = [i for i in range(len(word2) + 1)] for i in range(1, len(word1) + 1): for j in range(1, len(word2) + 1): deletion = distance[i - 1][j] + 1 addition = distance[i][j - 1] + 1 substitution = distance[i - 1][j - 1] if word1[i - 1] != word2[j - 1]: substitution += 1 distance[i].append(min(deletion, addition, substitution)) return distance[-1][-1]About
Python solution for Leetcode. Moved tohttps://github.com/jw2013/Leetcode-Py
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