From 1fcb8402232e4db9fb1af3312232f7c2e3f26ee5 Mon Sep 17 00:00:00 2001
From: tw2665 <55668073+tw2665@users.noreply.github.com>
Date: Tue, 18 May 2021 15:45:10 -0400
Subject: [PATCH] =?UTF-8?q?Update=200454.=E5=9B=9B=E6=95=B0=E7=9B=B8?=
 =?UTF-8?q?=E5=8A=A0II.md?=
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---
 problems/0454.四数相加II.md | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md
index a2ef928b..ad928a3f 100644
--- a/problems/0454.四数相加II.md
+++ b/problems/0454.四数相加II.md
@@ -121,6 +121,37 @@ class Solution {
 
 Python：
 
+```
+class Solution(object):
+    def fourSumCount(self, nums1, nums2, nums3, nums4):
+        """
+        :type nums1: List[int]
+        :type nums2: List[int]
+        :type nums3: List[int]
+        :type nums4: List[int]
+        :rtype: int
+        """
+        # use a dict to store the elements in nums1 and nums2 and their sum
+        hashmap = dict()
+        for n1 in nums1:
+            for n2 in nums2:
+                if n1 + n2 in hashmap:
+                    hashmap[n1+n2] += 1
+                else:
+                    hashmap[n1+n2] = 1
+        
+        # if the -(a+b) exists in nums3 and nums4, we shall add the count
+        count = 0
+        for n3 in nums3:
+            for n4 in nums4:
+                key = - n3 - n4
+                if key in hashmap:
+                    count += hashmap[key]
+        return count
+                
+
+```
+
 
 Go：