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LeetCode solutions

1861. Building Boxes

My accepted C++ solution to LeetCode problem 1861, Building Boxes, running in 0ms.

  • Difficulty: Hard
  • C++
  • Runtime 0ms
  • Memory 7.9MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

C++

Accepted on LeetCode — runtime 0ms, memory 7.9MB, accepted 2025-12-27.

cpp
class Solution {
    public:
    int minimumBoxes(int n) {
        // Find largest triangular pyramid that fits
        // Total boxes in pyramid of height h = h*(h+1)*(h+2)/6
        // Floor boxes = h*(h+1)/2

        long long total = 0, floor_boxes = 0, h = 0;

        // Build complete pyramid
        while (total + (h + 1) * (h + 2) / 2 <= n) {
            h++;
            floor_boxes = h * (h + 1) / 2;
            total += h * (h + 1) / 2;
        }

        // Add additional floor boxes one by one
        long long extra = 0, add = 0;
        while (total < n) {
            add++;
            extra += add;
            total += add;
        }

        return floor_boxes + add;
    }
};

Source