class Solution {
public:
vector<int> fairCandySwap(vector<int>& A, vector<int>& B)
{
int diff = 0; //A集合元素和与B集合元素和的差值
unordered_set<int> dicB; //B元素的哈希集合
for (auto a : A) diff += a;
for (auto b : B) {
diff -= b;
dicB.insert(b);
}
for (auto a : A) {
if (dicB.count(a - diff / 2))
return {a, a - diff / 2};
}
return {};
}
};