Leet Code Daily 2024-05-23 - The number of Beautiful Subsets

class Solution {
public:
    int dfs(vector<int>& nums, unordered_map<int, int>& cnt, int i, int k) {
        if (i == nums.size()) {
            return cnt.empty() ? 0 : 1;
        }
        int ret = dfs(nums, cnt, i + 1, k);
        if (cnt[nums[i] + k] == 0 && cnt[nums[i] - k] == 0) {
            cnt[nums[i]]++;
            ret += dfs(nums, cnt, i + 1, k);
            cnt[nums[i]]--;
        }
        return ret;
    }

    int beautifulSubsets(vector<int>& nums, int k) {
        unordered_map<int, int> cnt;
        return dfs(nums, cnt, 0, k);
    }
};