LeetCode Solutions
class Solution {
public:
int fourSumCount(vector<int>& A, vector<int>& B,
vector<int>& C, vector<int>& D) {
int ans = 0;
unordered_map<int, int> count;
for (const int a : A)
for (const int b : B)
++count[a + b];
for (const int c : C)
for (const int d : D)
if (count.count(-c - d))
ans += count[-c - d];
return ans;
}
};
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class Solution {
public int fourSumCount(int[] A, int[] B, int[] C, int[] D) {
int ans = 0;
Map<Integer, Integer> count = new HashMap<>();
for (final int a : A)
for (final int b : B)
count.put(a + b, count.getOrDefault(a + b, 0) + 1);
for (final int c : C)
for (final int d : D)
if (count.containsKey(-c - d))
ans += count.get(-c - d);
return ans;
}
}
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class Solution:
def fourSumCount(self, A: List[int], B: List[int], C: List[int], D: List[int]) -> int:
count = Counter(a + b for a in A for b in B)
return sum(count[-c - d] for c in C for d in D)
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