Fix flake8 related issues

Python/01-matrix.py

@@ -4,7 +4,7 @@
 # Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell.
 # The distance between two adjacent cells is 1.
 #
-# Example 1: 
+# Example 1:
 #
 # Input:
 # 0 0 0
@@ -16,7 +16,7 @@
 # 0 1 0
 # 0 0 0
 #
-# Example 2: 
+# Example 2:
 #
 # Input:
 # 0 0 0
@@ -33,6 +33,9 @@
 # There are at least one 0 in the given matrix.
 # The cells are adjacent in only four directions: up, down, left and right.
 
+import collections
+
+
 class Solution(object):
     def updateMatrix(self, matrix):
         """
@@ -57,7 +60,7 @@ def updateMatrix(self, matrix):
                         continue
                 queue.append((i, j))
                 matrix[i][j] = matrix[cell[0]][cell[1]]+1
-        
+
         return matrix
 
 

Python/4sum-ii.py

@@ -24,6 +24,9 @@
 # 1. (0, 0, 0, 1) -> A[0] + B[0] + C[0] + D[1] = 1 + (-2) + (-1) + 2 = 0
 # 2. (1, 1, 0, 0) -> A[1] + B[1] + C[0] + D[0] = 2 + (-1) + (-1) + 0 = 0
 
+import collections
+
+
 class Solution(object):
     def fourSumCount(self, A, B, C, D):
         """

Python/4sum.py

@@ -1,7 +1,7 @@
 # Time:  O(n^3)
 # Space: O(1)
 
-# Given an array S of n integers, 
+# Given an array S of n integers,
 # are there elements a, b, c, and d in S such that a + b + c + d = target?
 # Find all unique quadruplets in the array which gives the sum of target.
 #
@@ -16,6 +16,9 @@
 #    (-2,  0, 0, 2)
 #
 
+import collections
+
+
 # Two pointer solution. (1356ms)
 class Solution(object):
     def fourSum(self, nums, target):
@@ -62,7 +65,7 @@ def fourSum(self, nums, target):
         """
         nums, result, lookup = sorted(nums), [], collections.defaultdict(list)
         for i in xrange(0, len(nums) - 1):
-            for j in xrange(i + 1, len(nums)): 
+            for j in xrange(i + 1, len(nums)):
                 is_duplicated = False
                 for [x, y] in lookup[nums[i] + nums[j]]:
                     if nums[x] == nums[i]:
@@ -95,7 +98,7 @@ def fourSum(self, nums, target):
         """
         nums, result, lookup = sorted(nums), [], collections.defaultdict(list)
         for i in xrange(0, len(nums) - 1):
-            for j in xrange(i + 1, len(nums)): 
+            for j in xrange(i + 1, len(nums)):
                 lookup[nums[i] + nums[j]].append([i, j])
 
         for i in lookup.keys():

Python/accounts-merge.py

@@ -16,20 +16,20 @@
 # The accounts themselves can be returned in any order.
 #
 # Example 1:
-# Input: 
+# Input:
 # accounts = [["John", "[email protected]", "[email protected]"],
 #             ["John", "[email protected]"],
 #             ["John", "[email protected]", "[email protected]"],
 #             ["Mary", "[email protected]"]]
 # Output: [["John", '[email protected]', '[email protected]', '[email protected]'],
 #          ["John", "[email protected]"], ["Mary", "[email protected]"]]
 #
-# Explanation: 
+# Explanation:
 # The first and third John's are the same person as they have the common email "[email protected]".
 # The second John and Mary are different people as none of their email addresses are used by other accounts.
 # We could return these lists in any order,
 # for example the answer [['Mary', '[email protected]'],
-#                         ['John', '[email protected]'], 
+#                         ['John', '[email protected]'],
 #                         ['John', '[email protected]', '[email protected]', '[email protected]']]
 # would still be accepted.
 #
@@ -39,14 +39,17 @@
 # The length of accounts[i] will be in the range [1, 10].
 # The length of accounts[i][j] will be in the range [1, 30].
 
+import collections
+
+
 class UnionFind(object):
     def __init__(self):
         self.set = []
 
     def get_id(self):
         self.set.append(len(self.set))
         return len(self.set)-1
-        
+
     def find_set(self, x):
         if self.set[x] != x:
             self.set[x] = self.find_set(self.set[x])  # path compression.

Python/add-bold-tag-in-string.py

@@ -1,6 +1,9 @@
 # Time:  O(n * d * l), l is the average string length
 # Space: O(n)
 
+import collections
+
+
 # 59ms
 class Solution(object):
     def addBoldTag(self, s, dict):
@@ -25,7 +28,7 @@ def addBoldTag(self, s, dict):
                 result.append("</b>");
         return "".join(result)
 
-    
+
 # Time:  O(n * l), l is the average string length
 # Space: O(t)    , t is the size of trie
 # trie solution, 439ms

Python/alien-dictionary.py

@@ -1,41 +1,50 @@
 # Time:  O(n)
 # Space: O(|V|+|E|) = O(26 + 26^2) = O(1)
 
+import collections
+
+try:
+    xrange          # Python 2
+except NameError:
+    xrange = range  # Python 3
+
+
 # BFS solution.
 class Solution(object):
     def alienOrder(self, words):
         """
         :type words: List[str]
         :rtype: str
         """
-        result, zero_in_degree_queue, in_degree, out_degree = [], collections.deque(), {}, {}
-        nodes = sets.Set()
+        result, in_degree, out_degree = [], {}, {}
+        zero_in_degree_queue = collections.deque()
+        nodes = set()
         for word in words:
             for c in word:
                 nodes.add(c)
-        
+
         for i in xrange(1, len(words)):
-            if len(words[i-1]) > len(words[i]) and \
-                words[i-1][:len(words[i])] == words[i]:
-                    return ""
+            if (len(words[i-1]) > len(words[i]) and
+                    words[i-1][:len(words[i])] == words[i]):
+                return ""
             self.findEdges(words[i - 1], words[i], in_degree, out_degree)
-        
+
         for node in nodes:
             if node not in in_degree:
                 zero_in_degree_queue.append(node)
-        
+
         while zero_in_degree_queue:
             precedence = zero_in_degree_queue.popleft()
             result.append(precedence)
-            
+
             if precedence in out_degree:
                 for c in out_degree[precedence]:
                     in_degree[c].discard(precedence)
                     if not in_degree[c]:
                         zero_in_degree_queue.append(c)
-            
+
                 del out_degree[precedence]
-        
+
         if out_degree:
             return ""
 
@@ -48,9 +57,9 @@ def findEdges(self, word1, word2, in_degree, out_degree):
         for i in xrange(str_len):
             if word1[i] != word2[i]:
                 if word2[i] not in in_degree:
-                    in_degree[word2[i]] = sets.Set()
+                    in_degree[word2[i]] = set()
                 if word1[i] not in out_degree:
-                    out_degree[word1[i]] = sets.Set()
+                    out_degree[word1[i]] = set()
                 in_degree[word2[i]].add(word1[i])
                 out_degree[word1[i]].add(word2[i])
                 break
@@ -64,16 +73,16 @@ def alienOrder(self, words):
         :rtype: str
         """
         # Find ancestors of each node by DFS.
-        nodes, ancestors = sets.Set(), {}
+        nodes, ancestors = set(), {}
         for i in xrange(len(words)):
             for c in words[i]:
                 nodes.add(c)
         for node in nodes:
             ancestors[node] = []
         for i in xrange(1, len(words)):
-            if len(words[i-1]) > len(words[i]) and \
-                words[i-1][:len(words[i])] == words[i]:
-                    return ""
+            if (len(words[i-1]) > len(words[i]) and
+                    words[i-1][:len(words[i])] == words[i]):
+                return ""
             self.findEdges(words[i - 1], words[i], ancestors)
 
         # Output topological order by DFS.
@@ -82,7 +91,7 @@ def alienOrder(self, words):
         for node in nodes:
             if self.topSortDFS(node, node, ancestors, visited, result):
                 return ""
-        
+
         return "".join(result)
 
 

Python/arithmetic-slices-ii-subsequence.py

@@ -42,6 +42,9 @@
 # [2,4,6,8,10]
 # [2,6,10]
 
+import collections
+
+
 class Solution(object):
     def numberOfArithmeticSlices(self, A):
         """

Python/arranging-coins.py

@@ -30,6 +30,9 @@
 #
 # Because the 4th row is incomplete, we return 3.
 
+import math
+
+
 class Solution(object):
     def arrangeCoins(self, n):
         """

Python/basic-calculator-iv.py

@@ -15,7 +15,7 @@
 #   have a leading coefficient or unary operator like "2x" or "-x".
 #
 # Expressions are evaluated in the usual order:
-# brackets first, then multiplication, then addition and subtraction. 
+# brackets first, then multiplication, then addition and subtraction.
 # For example, expression = "1 + 2 * 3" has an answer of ["7"].
 #
 # The format of the output is as follows:
@@ -26,9 +26,9 @@
 #   counting multiplicity. (For example, "a*a*b*c" has degree 4.)
 #   We write the largest degree terms of our answer first,
 #   breaking ties by lexicographic order ignoring the leading coefficient of the term.
-# - The leading coefficient of the term is placed directly to the left with an asterisk separating it 
+# - The leading coefficient of the term is placed directly to the left with an asterisk separating it
 #   from the variables (if they exist.) A leading coefficient of 1 is still printed.
-# - An example of a well formatted answer is ["-2*a*a*a", "3*a*a*b", "3*b*b", "4*a", "5*c", "-6"] 
+# - An example of a well formatted answer is ["-2*a*a*a", "3*a*a*b", "3*b*b", "4*a", "5*c", "-6"]
 # - Terms (including constant terms) with coefficient 0 are not included.
 #    For example, an expression of "0" has an output of [].
 #
@@ -52,7 +52,7 @@
 #
 # Input: expression = "((a - b) * (b - c) + (c - a)) * ((a - b) + (b - c) * (c - a))",
 # evalvars = [], evalints = []
-# Output: 
+# Output:
 # ["-1*a*a*b*b","2*a*a*b*c","-1*a*a*c*c","1*a*b*b*b","-1*a*b*b*c","-1*a*b*c*c",
 #  "1*a*c*c*c","-1*b*b*b*c","2*b*b*c*c","-1*b*c*c*c","2*a*a*b","-2*a*a*c","-2*a*b*b",
 #  "2*a*c*c","1*b*b*b","-1*b*b*c","1*b*c*c","-1*c*c*c","-1*a*a","1*a*b","1*a*c","-1*b*c"]
@@ -61,6 +61,10 @@
 # - expression will have length in range [1, 1000].
 # - evalvars, evalints will have equal lengths in range [0, 1000].
 
+import collections
+import itertools
+
+
 class Poly(collections.Counter):
     def __init__(self, expr=None):
         if expr is None:
@@ -94,9 +98,9 @@ def merge(k1, k2):
                     i += 1
                 else:
                     result.append(k2[j])
-                    j += 1   
+                    j += 1
             return result
-        
+
         result = Poly()
         for k1, v1 in self.items():
             for k2, v2 in other.items():
@@ -119,8 +123,8 @@ def to_list(self):
         return ["*".join((str(v),) + k) \
                 for k, v in sorted(self.items(), key=lambda(k, _): (-len(k), k)) \
                 if v]
-    
-    
+
+
 class Solution(object):
     def basicCalculatorIV(self, expression, evalvars, evalints):
         """
@@ -138,7 +142,7 @@ def compute(operands, operators):
                 operands.append(left - right)
             elif op == '*':
                 operands.append(left * right)
-             
+
         def parse(s):
             if not s:
                 return Poly()
@@ -163,6 +167,6 @@ def parse(s):
             while operators:
                 compute(operands, operators)
             return operands[-1]
-        
+
         lookup = dict(itertools.izip(evalvars, evalints))
         return parse(expression).eval(lookup).to_list()

Python/binary-tree-vertical-order-traversal.py

@@ -8,6 +8,9 @@
 #         self.left = None
 #         self.right = None
 
+import collections
+
+
 # BFS + hash solution.
 class Solution(object):
     def verticalOrder(self, root):

Python/bold-words-in-string.py

@@ -1,6 +1,9 @@
 # Time:  O(n * l), n is the length of S, l is the average length of words
 # Space: O(t)    , t is the size of trie
 
+import collections
+
+
 class Solution(object):
     def boldWords(self, words, S):
         """

Python/brick-wall.py

@@ -15,7 +15,7 @@
 # in which case the line will obviously cross no bricks.
 #
 # Example:
-# Input: 
+# Input:
 # [[1,2,2,1],
 #  [3,1,2],
 #  [1,3,2],
@@ -30,6 +30,9 @@
 # The height of wall is in range [1,10,000].
 # Total number of bricks of the wall won't exceed 20,000.
 
+import collections
+
+
 class Solution(object):
     def leastBricks(self, wall):
         """