struct T {
int i;
int j;
int sum; // nums1[i] + nums2[j]
T(int i, int j, int sum) : i(i), j(j), sum(sum) {}
};
class Solution {
public:
vector<vector<int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2,
int k) {
vector<vector<int>> ans;
auto compare = [&](const T& a, const T& b) { return a.sum > b.sum; };
priority_queue<T, vector<T>, decltype(compare)> minHeap(compare);
for (int i = 0; i < k && i < nums1.size(); ++i)
minHeap.emplace(i, 0, nums1[i] + nums2[0]);
while (!minHeap.empty() && ans.size() < k) {
const auto [i, j, _] = minHeap.top();
minHeap.pop();
ans.push_back({nums1[i], nums2[j]});
if (j + 1 < nums2.size())
minHeap.emplace(i, j + 1, nums1[i] + nums2[j + 1]);
}
return ans;
}
};