From 5cff41ab09e2b3866f3245c3d06d61b3b432f485 Mon Sep 17 00:00:00 2001
From: jianghongcheng <35664721+jianghongcheng@users.noreply.github.com>
Date: Fri, 5 May 2023 20:53:12 -0500
Subject: [PATCH] =?UTF-8?q?Update=200454.=E5=9B=9B=E6=95=B0=E7=9B=B8?=
 =?UTF-8?q?=E5=8A=A0II.md?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 problems/0454.四数相加II.md | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md
index 7818c02b..31f0504f 100644
--- a/problems/0454.四数相加II.md
+++ b/problems/0454.四数相加II.md
@@ -149,7 +149,29 @@ class Solution(object):
  
 
 ```
-（版本二）使用 defaultdict
+（版本二） 使用字典
+```python
+class Solution(object):
+    def fourSumCount(self, nums1, nums2, nums3, nums4):
+        # 使用字典存储nums1和nums2中的元素及其和
+        hashmap = dict()
+        for n1 in nums1:
+            for n2 in nums2:
+                hashmap[n1+n2] = hashmap.get(n1+n2, 0) + 1
+        
+        # 如果 -(n1+n2) 存在于nums3和nums4, 存入结果
+        count = 0
+        for n3 in nums3:
+            for n4 in nums4:
+                key = - n3 - n4
+                if key in hashmap:
+                    count += hashmap[key]
+        return count
+ 
+ 
+
+```
+（版本三）使用 defaultdict
 ```python
 from collections import defaultdict 
 class Solution: