1889. Minimum Space Wasted From Packaging

You have n packages that you are trying to place in boxes, one package in each box. There are m suppliers that each produce boxes of different sizes (with infinite supply). A package can be placed in a box if the size of the package is less than or equal to the size of the box.

The package sizes are given as an integer array packages, where packages[i] is the size of the ith package. The suppliers are given as a 2D integer array boxes, where boxes[j] is an array of box sizes that the jth supplier produces.

You want to choose a single supplier and use boxes from them such that the total wasted space is minimized. For each package in a box, we define the space wasted to be size of the box - size of the package. The total wasted space is the sum of the space wasted in all the boxes.

• For example, if you have to fit packages with sizes [2,3,5] and the supplier offers boxes of sizes [4,8], you can fit the packages of size-2 and size-3 into two boxes of size-4 and the package with size-5 into a box of size-8. This would result in a waste of (4-2) + (4-3) + (8-5) = 6.

Return the minimum total wasted space by choosing the box supplier optimally, or -1 if it is impossible to fit all the packages inside boxes. Since the answer may be large, return it modulo 109 + 7.

class Solution {
public:
    int minWastedSpace(vector<int>& P, vector<vector<int>>& B) {
        long long res = LLONG_MAX, mod = 1e9 + 7;
        sort(begin(P), end(P));
        for(auto& b : B) {
            sort(begin(b), end(b));
            long long sum = 0;
            if(b.back() < P.back()) continue;
            long long i = 0, j = 0, k = 0, n = P.size(), m = b.size();
            while(i < m and j < n and sum < res) {
                k = upper_bound(begin(P) + j, end(P), b[i]) - begin(P);
                sum += b[i++] * (k - j);
                j = k;
            }
            
            res = min(res, sum);
        }
        return res == LLONG_MAX ? -1 : (res - accumulate(begin(P), end(P), 0ll)) % mod;
    }
};