Choose K Elements With Maximum Sum — C++

// Time:  O(nlogn)
// Space: O(n)

// sort, greedy, two pointers, heap
class Solution {
public:
    vector<long long> findMaxSum(vector<int>& nums1, vector<int>& nums2, int k) {
        vector<long long> result(size(nums1));
        priority_queue<int, vector<int>, greater<int>> min_heap;
        vector<int> idxs(size(nums1));
        iota(begin(idxs), end(idxs), 0);
        sort(begin(idxs), end(idxs), [&](const auto& a, const auto& b) {
            return nums1[a] < nums1[b];
        });
        int64_t total = 0;
        for (int i = 0, j = 0; i < size(idxs); ++i) {
            for (; nums1[idxs[j]] < nums1[idxs[i]]; ++j) {
                total += nums2[idxs[j]];
                min_heap.emplace(nums2[idxs[j]]);
                if (size(min_heap) == k + 1) {
                    total -= min_heap.top(); min_heap.pop();
                }
            }
            result[idxs[i]] = total;
        }
        return result;
    }
};