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: