Kth Ancestor of a Tree Node
<p>You are given a tree with <code>n</code> nodes numbered from <code>0</code> to <code>n - 1</code> in the form of a parent array <code>parent</code> where <code>parent[i]</code> is the parent of <code>i<sup>th</sup></code> node. The root of the tree is node <code>0</code>. Find the <code>k<sup>th</sup></code> ancestor of a given node.</p>

<p>The <code>k<sup>th</sup></code> ancestor of a tree node is the <code>k<sup>th</sup></code> node in the path from that node to the root node.</p>

<p>Implement the <code>TreeAncestor</code> class:</p>

<ul>
	<li><code>TreeAncestor(int n, int[] parent)</code> Initializes the object with the number of nodes in the tree and the parent array.</li>
	<li><code>int getKthAncestor(int node, int k)</code> return the <code>k<sup>th</sup></code> ancestor of the given node <code>node</code>. If there is no such ancestor, return <code>-1</code>.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/1400-1499/1483.Kth%20Ancestor%20of%20a%20Tree%20Node/images/1528_ex1.png" style="width: 396px; height: 262px;" />
<pre>
<strong>Input</strong>
[&quot;TreeAncestor&quot;, &quot;getKthAncestor&quot;, &quot;getKthAncestor&quot;, &quot;getKthAncestor&quot;]
[[7, [-1, 0, 0, 1, 1, 2, 2]], [3, 1], [5, 2], [6, 3]]
<strong>Output</strong>
[null, 1, 0, -1]

<strong>Explanation</strong>
TreeAncestor treeAncestor = new TreeAncestor(7, [-1, 0, 0, 1, 1, 2, 2]);
treeAncestor.getKthAncestor(3, 1); // returns 1 which is the parent of 3
treeAncestor.getKthAncestor(5, 2); // returns 0 which is the grandparent of 5
treeAncestor.getKthAncestor(6, 3); // returns -1 because there is no such ancestor</pre>

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

<ul>
	<li><code>1 &lt;= k &lt;= n &lt;= 5 * 10<sup>4</sup></code></li>
	<li><code>parent.length == n</code></li>
	<li><code>parent[0] == -1</code></li>
	<li><code>0 &lt;= parent[i] &lt; n</code> for all <code>0 &lt; i &lt; n</code></li>
	<li><code>0 &lt;= node &lt; n</code></li>
	<li>There will be at most <code>5 * 10<sup>4</sup></code> queries.</li>
</ul>
Tree; Depth-First Search; Breadth-First Search; Design; Binary Search; Dynamic Programming
type TreeAncestor struct {
	p [][18]int
}

func Constructor(n int, parent []int) TreeAncestor {
	p := make([][18]int, n)
	for i, fa := range parent {
		p[i][0] = fa
		for j := 1; j < 18; j++ {
			p[i][j] = -1
		}
	}
	for j := 1; j < 18; j++ {
		for i := range p {
			if p[i][j-1] == -1 {
				continue
			}
			p[i][j] = p[p[i][j-1]][j-1]
		}
	}
	return TreeAncestor{p}
}

func (this *TreeAncestor) GetKthAncestor(node int, k int) int {
	for i := 17; i >= 0; i-- {
		if k>>i&1 == 1 {
			node = this.p[node][i]
			if node == -1 {
				break
			}
		}
	}
	return node
}

/**
 * Your TreeAncestor object will be instantiated and called as such:
 * obj := Constructor(n, parent);
 * param_1 := obj.GetKthAncestor(node,k);
 */