Merge pull request #1792 from PeterLijunfeng/master

0704Python版本严格参照C++写法及次序，并追加注释

problems/0704.二分查找.md

@@ -204,18 +204,18 @@ class Solution {
 ```python
 class Solution:
     def search(self, nums: List[int], target: int) -> int:
-        left, right = 0, len(nums) - 1
+        left, right = 0, len(nums) - 1  # 定义target在左闭右闭的区间里，[left, right]
-        
-        while left <= right:
-            middle = (left + right) // 2
 
-            if nums[middle] < target:
+        while left <= right:
-                left = middle + 1
+            middle = left + (right - left) // 2
-            elif nums[middle] > target:
+            
-                right = middle - 1
+            if nums[middle] > target:
+                right = middle - 1  # target在左区间，所以[left, middle - 1]
+            elif nums[middle] < target:
+                left = middle + 1  # target在右区间，所以[middle + 1, right]
             else:
-                return middle
+                return middle  # 数组中找到目标值，直接返回下标
-        return -1
+        return -1  # 未找到目标值
 ```
 
 （版本二）左闭右开区间
@@ -223,18 +223,18 @@ class Solution:
 ```python
 class Solution:
     def search(self, nums: List[int], target: int) -> int:
-        left, right = 0, len(nums)
+        left, right = 0, len(nums)  # 定义target在左闭右开的区间里，即：[left, right)
 
-        while left < right:
+        while left < right:  # 因为left == right的时候，在[left, right)是无效的空间，所以使用 <
-            middle = (left + right) // 2
+            middle = left + (right - left) // 2
 
-            if nums[middle] < target:
+            if nums[middle] > target:
-                left = middle + 1
+                right = middle  # target 在左区间，在[left, middle)中
-            elif nums[middle] > target:
+            elif nums[middle] < target:
-                right = middle
+                left = middle + 1  # target 在右区间，在[middle + 1, right)中
             else:
-                return middle
+                return middle  # 数组中找到目标值，直接返回下标
-        return -1
+        return -1  # 未找到目标值
 ```
 
 **Go：**