2020-07-10

Author: JiayangWu

1.两数之和/1-两数之和.py

@@ -1,12 +1,7 @@
-class Solution(object):
-    def twoSum(self, nums, target):
-        """
-        :type nums: List[int]
-        :type target: int
-        :rtype: List[int]
-        """
-        dic = {}
-        for i, num in enumerate(nums):
-            if target - num in dic:
-                return [dic[target - num], i]
-            dic[num] = i
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        hashmap = {}
+        for index, item in enumerate(nums):
+            if target - item in hashmap:
+                return hashmap[target-item],index
+            hashmap[item] = index

315.计算右侧小于当前元素的个数/315-计算右侧小于当前元素的个数.py

@@ -11,7 +11,6 @@ def countSmaller(self, nums):
         :type nums: List[int]
         :rtype: List[int]
         """
-        
         # 从左往右处理，右边是未知的，所以不好弄
         # 从右往左处理，则对于每个数，其右边的数都已知
         res = [0 for _ in nums]
@@ -21,15 +20,13 @@ def countSmaller(self, nums):
         return res[::-1]
 
     def insert(self, root, val, i, res):
-        if not root:
+        if not root: #如果当前root为空
             root = TreeNode(val)
-        elif root.val >= val:
+        elif root.val >= val: # 如果应该插入左子树
             root.left_subtree_cnt += 1
             root.left = self.insert(root.left, val, i, res)
-        elif root.val < val:
-            res[i] += root.left_subtree_cnt + 1
+        elif root.val < val: # 如果应该插入右子树
+            res[i] += root.left_subtree_cnt + 1 # 1 代表当前root
             root.right = self.insert(root.right, val, i, res)
 
-        return root
-            
-            
+        return root