g1401_1500.s1483_kth_ancestor_of_a_tree_node

Class TreeAncestor

java.lang.Object

g1401_1500.s1483_kth_ancestor_of_a_tree_node.TreeAncestor

public class TreeAncestor
extends Object

1483 - Kth Ancestor of a Tree Node.

Hard

You are given a tree with n nodes numbered from 0 to n - 1 in the form of a parent array parent where parent[i] is the parent of ith node. The root of the tree is node 0. Find the kth ancestor of a given node.

The kth ancestor of a tree node is the kth node in the path from that node to the root node.

Implement the TreeAncestor class:

• TreeAncestor(int n, int[] parent) Initializes the object with the number of nodes in the tree and the parent array.
• int getKthAncestor(int node, int k) return the kth ancestor of the given node node. If there is no such ancestor, return -1.

Example 1:

Input [“TreeAncestor”, “getKthAncestor”, “getKthAncestor”, “getKthAncestor”] [[7, [-1, 0, 0, 1, 1, 2, 2]], [3, 1], [5, 2], [6, 3]]

Output: [null, 1, 0, -1]

Explanation:

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

Constraints:

• 1 <= k <= n <= 5 * 104
• parent.length == n
• parent[0] == -1
• 0 <= parent[i] < n for all 0 < i < n
• 0 <= node < n
• There will be at most 5 * 104 queries.

Constructor Summary

Constructors

Constructor and Description
TreeAncestor(int n, int[] parent)

Method Summary

Modifier and Type	Method and Description
int	getKthAncestor(int node, int k)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TreeAncestor

public TreeAncestor(int n,
                    int[] parent)

Method Detail

getKthAncestor

public int getKthAncestor(int node,
                          int k)