Merge pull request #662 from GHumorBS/master

更新0454.四数相加II.md的python算法

problems/0454.四数相加II.md

@@ -161,15 +161,9 @@ class Solution(object):
 #         count=0
 #         for x3 in nums3:
 #             for x4 in nums4:
-#                 key = -x3-x4
-#                 value = hashmap.get(key)
-
-                  # dict的get方法会返回None（key不存在）或者key对应的value
-                  # 所以如果value==0，就会继续执行or，count+0，否则就会直接加value
-                  # 这样就不用去写if判断了
-            
-#                 count += value or 0
-                
+#                 key = 0 - x3 - x4
+#                 value = hashmap[key]  # 若差值(key)不存在，则value被赋值0
+#                 count += value                
 #         return count
 
 ```