Minimum Space Wasted From Packaging — C++

// Time:  O(mlogm + nlogn + mlogn)
// Space: O(1)

class Solution {
public:
    int minWastedSpace(vector<int>& packages, vector<vector<int>>& boxes) {
        static const int MOD = 1e9 + 7;
        static const int64_t INF = numeric_limits<int64_t>::max();

        sort(begin(packages), end(packages));
        int64_t result = INF;
        for (auto& box : boxes) {
            sort(begin(box), end(box));
            if (box.back() < packages.back()) {
                continue;
            }
            int64_t curr = 0;
            auto left = cbegin(packages);
            for (const auto& b : box) {
                auto right = upper_bound(left, cend(packages), b);
                curr += b * (right - left);
                left = right;
            }
            result = min(result, curr);
        }
        int64_t total = accumulate(cbegin(packages), cend(packages), 0LL);
        return result != INF ? (result - total) % MOD : -1;
    }
};