- Difficulty: Hard
- Tags: LeetCode, Hard, Tree, Depth-First Search, Breadth-First Search, Design, Binary Search, Dynamic Programming, leetcode-1483, O(n * logh), DP, Binary Lifting
Problem
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 thekth
ancestor of the given nodenode
. 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 all0 < i < n
0 <= node < n
- There will be at most
5 * 104
queries.