Subsets
<p>Given an integer array <code>nums</code> of <strong>unique</strong> elements, return <em>all possible</em> <span data-keyword="subset"><em>subsets</em></span> <em>(the power set)</em>.</p>

<p>The solution set <strong>must not</strong> contain duplicate subsets. Return the solution in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,3]
<strong>Output:</strong> [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [0]
<strong>Output:</strong> [[],[0]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10</code></li>
	<li><code>-10 &lt;= nums[i] &lt;= 10</code></li>
	<li>All the numbers of&nbsp;<code>nums</code> are <strong>unique</strong>.</li>
</ul>
Bit Manipulation; Array; Backtracking
impl Solution {
    fn dfs(i: usize, t: &mut Vec<i32>, ans: &mut Vec<Vec<i32>>, nums: &Vec<i32>) {
        if i == nums.len() {
            ans.push(t.clone());
            return;
        }
        Self::dfs(i + 1, t, ans, nums);
        t.push(nums[i]);
        Self::dfs(i + 1, t, ans, nums);
        t.pop();
    }

    pub fn subsets(nums: Vec<i32>) -> Vec<Vec<i32>> {
        let mut ans = Vec::new();
        Self::dfs(0, &mut Vec::new(), &mut ans, &nums);
        ans
    }
}
