LeetCode/cpp/largest-divisble-subset.cpp

#include <algorithm>
#include <cassert>
#include <vector>

struct Solution {
    std::vector<int> largestDivisibleSubset(std::vector<int> nums) {
        std::sort(nums.begin(), nums.end());

        solver s(nums);
        s.solve();
        return s.result;
    }

  private:
    struct solver {
        const std::vector<int> &nums;
        int n;
        std::vector<std::size_t> dp;
        std::vector<int> tmp;
        std::vector<int> result;

        solver(const std::vector<int> &nums)
            : nums(nums), n(nums.size()), dp(nums.size() + 1, 0) {}

        void solve() { solve(0); }

        void solve(int i) {
            if (i >= n) {
                if (tmp.size() > result.size()) {
                    result = tmp;
                }

                return;
            }

            if (tmp.empty() ||
                (tmp.size() > dp[i] && nums[i] % tmp.back() == 0)) {
                dp[i] = std::max(dp[i], tmp.size());

                tmp.push_back(nums[i]);
                solve(i + 1);
                tmp.pop_back();
            }

            solve(i + 1);
        }
    };
};

int main() {
    Solution s;

    assert(
        (s.largestDivisibleSubset(std::vector{1, 2, 3}) == std::vector{1, 2}));
    assert((s.largestDivisibleSubset(std::vector{1, 2, 4, 8}) ==
            std::vector{1, 2, 4, 8}));
    assert((s.largestDivisibleSubset(std::vector{3, 4, 16, 8}) ==
            std::vector{4, 8, 16}));

    return 0;
}