2019-08-16

Author: JiayangWu

0236.二叉树的最近公共祖先/0236-二叉树的最近公共祖先.py

@@ -13,20 +13,16 @@ def lowestCommonAncestor(self, root, p, q):
         :type q: TreeNode
         :rtype: TreeNode
         """
-        
-        if not root or root == p or root == q:
+        if root in [p, q, None]:
             return root
         else:
             left = self.lowestCommonAncestor(root.left, p, q)
             right = self.lowestCommonAncestor(root.right, p, q)
 
-            if left and right: #一个在左子树，一个在右子树
+            if left and right:
                 return root
-            elif left:#都在左子树
+            elif left:
                 return left
-            elif right:#都在右子树
+            elif right:
                 return right
-            else:
-                return
-
-            
+                

0238.除自身以外数组的乘积/0238-除自身以外数组的乘积.py

@@ -4,16 +4,11 @@ def productExceptSelf(self, nums):
         :type nums: List[int]
         :rtype: List[int]
         """
-        l = len(nums)
-        res = [1] * l
-        for i in range(1,l):
-            res[i] = res[i - 1] *nums[i - 1]
-        
-        p = 1
-        for i in reversed(range(l)):
-            res[i] *= p
-            p *= nums[i]
-            
-        return res
-                
-        
+        res = [1] * len(nums)
+        for i in range(1, len(nums)):
+            res[i] = res[i - 1] * nums[i - 1]
+        tmp = 1
+        for i in range(len(nums) - 1, -1, -1):
+            res[i] *= tmp
+            tmp *= nums[i]
+        return res

0239.滑动窗口最大值/0239-滑动窗口最大值.py

@@ -7,20 +7,17 @@ def maxSlidingWindow(self, nums, k):
         """
         if not nums:
             return []
-        
-        window, res = list(), list()
-        for i, x in enumerate(nums):
-            
-            if window and window[0] <= i - k:
+
+        window = []
+        res = []
+        for i in range(len(nums)):
+            if window and window[0] <= i - k: #当前window头应该被弹出
                 window.pop(0)
-            while window and nums[window[-1]] < x:
 
+            while window and nums[window[-1]] < nums[i]: #比 nums[i] 小的都不要，因为只要窗口的最大值
                 window.pop()
 
             window.append(i)
-            
             if i >= k - 1:
                 res.append(nums[window[0]])
-                
-        return res
-        
+        return res

0240.搜索二维矩阵II/0240-搜索二维矩阵II.py

@@ -0,0 +1,16 @@
+class Solution(object):
+    def searchMatrix(self, matrix, target):
+        """
+        :type matrix: List[List[int]]
+        :type target: int
+        :rtype: bool
+        """
+        if not matrix or not matrix[0]:
+            return False
+        m, n = len(matrix), len(matrix[0])
+        
+        for i in range(m):
+            for j in range(n):
+                if matrix[i][j] == target:
+                    return True
+        return False

0242.有效的字母异位词/0242-有效的字母异位词.py

@@ -5,12 +5,4 @@ def isAnagram(self, s, t):
         :type t: str
         :rtype: bool
         """
-        hashmaps, hashmapt = dict(), dict()
-        for char in s:
-            hashmaps[char] = hashmaps.get(char, 0) + 1
-        
-        for char in t:
-            hashmapt[char] = hashmapt.get(char, 0) + 1
-            
-        return hashmaps == hashmapt
-        
+        return sorted(s) == sorted(t)