The family tree of Bob
Practice
4.1 (8 votes)
Algorithms
Depth first search
Graphs
Problem
35% Success 2579 Attempts 30 Points 3s Time Limit 1024MB Memory 1024 KB Max Code
Bob wants to know about his ancestors, therefore, he draws a graph of his family. In that graph, root is the eldest-known family member. The leaf node is a member who has no children.
You are given a \(Q\) query and \(N\) family members. They have to just print the \(k^{th}\) ancestors with respect to that query. A member can have only one parent.
Note: Print -1 if the query is incorrect, that is, if the \(k^{th}\) ancestor is not available. The root of the tree is 1.
Input format
- The first line contains two space-separated integers \(N\) and \(Q\) denoting the number of nodes and the number of queries.
- Next \(N- 1\) lines contain two space-separated integers \(u\) and \(v\) denoting an edge between node \(u\) and node \(v\).
- Next \(Q\) lines contain two space-separated integers \(u\) and \(k\).
Output format
For each query, print a single line containing one integer.
Constraints
\(1 ≤ N,\ Q ≤ 5e5\\ 0 ≤ k ≤ 5e5\)
Submissions
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