|
1 |
| -Leetcode |
2 |
| -=== |
3 |
| - |
4 |
| -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. |
| 1 | +This project is no longer maintained here. |
5 | 2 |
|
6 |
| -Feel free to submit pull requests for submitting more elegant solution. |
7 |
| - |
8 |
| -###List of idiomatic Python I prefer (as of now) |
9 |
| ---- |
10 |
| -- Prefer list comprehension over map / filter. |
11 |
| -``` |
12 |
| - # from Gray Code |
13 |
| -
|
14 |
| - # Bad |
15 |
| - def grayCode(self, n): |
16 |
| - return map(lambda x: (x / 2) ^ x, range(1 << n)) |
17 |
| -
|
18 |
| - # Idiomatic |
19 |
| - def grayCode(self, n): |
20 |
| - return [(x / 2) ^ x for x in range(1 << n)] |
21 |
| -``` |
22 |
| -- Prefer using `in` keyword over repetitive variable in conditional statement. |
23 |
| -``` |
24 |
| - # from Post Order Traversal |
25 |
| -
|
26 |
| - # Bad |
27 |
| - if parent.right == None or parent.right == prev |
28 |
| -
|
29 |
| - # Idiomatic |
30 |
| - if parent.right in (None, prev): |
31 |
| -``` |
32 |
| -- Prefer using docstring over single line comment when describing functionality of a method. |
33 |
| -``` |
34 |
| - # from Search Insert Position |
35 |
| -
|
36 |
| - # Bad |
37 |
| - # Iterative solution is also fine. |
38 |
| - def searchInsert(self, A, target): |
39 |
| -
|
40 |
| - # Idiomatic |
41 |
| - def searchInsert(self, A, target): |
42 |
| - """Iterative solution is also fine. |
43 |
| - """ |
44 |
| -``` |
45 |
| -- Prefer implicit evaluation of condition (e.g. `if`, `while`, etc.) over explicit comparison in condition. |
46 |
| -Notice empty list and dictionary will be evaluated to False, so that is very handy. |
47 |
| -``` |
48 |
| - # from Binary Tree Preorder Traversal |
49 |
| -
|
50 |
| - # Bad |
51 |
| - while len(stack) > 0: |
52 |
| - current = stack.pop() |
53 |
| -
|
54 |
| - # Idiomatic |
55 |
| - while stack: |
56 |
| - current = stack.pop() |
57 |
| -``` |
58 |
| -- Prefer `is None` over `== None`. Notice `is` looks for referential equality, and `None` is a singleton. |
59 |
| -The fundamental reason for this preference is much improved speed, and `==` can be overriden by `__eq__`. |
60 |
| -``` |
61 |
| - # from Binary Tree Preorder Traversal |
62 |
| -
|
63 |
| - # Bad |
64 |
| - if root == None: |
65 |
| -
|
66 |
| - # Idiomatic |
67 |
| - if root is None: |
68 |
| -``` |
69 |
| -One interesting side note in Python regarding this is on [Stackoverflow](http://stackoverflow.com/questions/306313/python-is-operator-behaves-unexpectedly-with-integers/306347). Trust me, that is worth your 60 seconds of time. But that only works in REPL though, not on a executable python file. |
70 |
| - |
71 |
| -READ THIS or above two rules will only do you harm: |
72 |
| -Sometimes you have to use `if foo is not None` over `if foo`. For example, if foo is 0, then `if 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 use `if foo is not None`, otherwise you can most likely use `if foo` if you know what you are doing. |
73 |
| -- Consider using enumerate when index accessing looks verbose |
74 |
| -``` |
75 |
| - # from Two Sum |
76 |
| -
|
77 |
| - # Bad |
78 |
| - for i in range(len(nums)): |
79 |
| - if target - nums[i] in lookup: |
80 |
| - return (lookup[target - nums[i]] + 1, i + 1) |
81 |
| - lookup[nums[i]] = i |
82 |
| -
|
83 |
| - # Idiomatic |
84 |
| - for i, num in enumerate(nums): |
85 |
| - if target - num in lookup: |
86 |
| - return (lookup[target - num] + 1, i + 1) |
87 |
| - lookup[num] = i |
88 |
| -``` |
89 |
| -- Readability counts. |
90 |
| - |
91 |
| - "Any fool can write code that a computer can understand. Good programmers write code that humans can understand." Martin Fowler is right. |
92 |
| -``` |
93 |
| - # from Edit Distance |
94 |
| -
|
95 |
| - # Bad |
96 |
| - def minDistance(self, word1, word2): |
97 |
| - distance = [[i] for i in range(len(word1) + 1)] |
98 |
| - distance[0] = [i for i in range(len(word2) + 1)] |
99 |
| - for i in range(1, len(word1) + 1): |
100 |
| - for j in range(1, len(word2) + 1): |
101 |
| - 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]))) |
102 |
| - return distance[-1][-1] |
103 |
| -
|
104 |
| - # Idiomatic |
105 |
| - def minDistance(self, word1, word2): |
106 |
| - distance = [[i] for i in range(len(word1) + 1)] |
107 |
| - distance[0] = [i for i in range(len(word2) + 1)] |
108 |
| - for i in range(1, len(word1) + 1): |
109 |
| - for j in range(1, len(word2) + 1): |
110 |
| - deletion = distance[i - 1][j] + 1 |
111 |
| - addition = distance[i][j - 1] + 1 |
112 |
| - substitution = distance[i - 1][j - 1] |
113 |
| - if word1[i - 1] != word2[j - 1]: |
114 |
| - substitution += 1 |
115 |
| - distance[i].append(min(deletion, addition, substitution)) |
116 |
| - return distance[-1][-1] |
| 3 | +Please go to https://github.com/jw2013/Leetcode-Py for latest update and for making pull request. Thanks! |
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