[LeetCode] 1710. Maximum Units on a Truck

 Problem : https://leetcode.com/problems/maximum-units-on-a-truck/

Greedily take the largest boxes first. Use heap to avoid sort all boxes.

class Solution:
    def maximumUnits(self, boxTypes: List[List[int]], truckSize: int) -> int:
        heap = [(-m, -n) for n, m in boxTypes]
        heapq.heapify(heap)
        
        result = 0
        
        while truckSize and heap:
            m, n = heapq.heappop(heap)
            m, n = -m, -n
            
            taken = min(truckSize, n)
            result += m * taken
            
            truckSize -= taken
            
        return result