Package g1401_1500.s1483_kth_ancestor_of_a_tree_node

Class 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 Detail

      • TreeAncestor

        public TreeAncestor​(int n,
                    int[] parent)

    • Method Detail

      • getKthAncestor

        public int getKthAncestor​(int node,
                          int k)