Maximum Safety
Practice
4 (22 votes)
Medium Hard
Problem
43% Success 412 Attempts 50 Points 3s Time Limit 256MB Memory 1024 KB Max Code

Kevin wants to hide from Marv in the city. The city consists of N junctions connected with roads. There are \(N-1\) roads, each of length 1. So the city is a tree. Root of this tree is junction 1.

For each of the next M days Kevin wants to hide in one of the junctions. Kevin knows that Marv is located in junction \(a_i\) on the i-th day. Kevin also believes that junction v is safe only if v is in the subtree of vertex \(b_i\). The safety of vertex v is equal to the distance between v and \(a_i\). Help Kevin to find the maximum safety possible for each day.

Input format:

The first line of input will contain an integer T, denoting the number of test cases.
Each test case starts with 2 numbers N and M. Next \(N-1\) lines contains 2 numbers \(u_i\) and \(v_i\) - junctions connected by a road. Next M lines contains 2 numbers \(a_i'\) and \(b_i'\). To find actual values of \(a_i\) and \(b_i\) Kevin does the following steps:

  • let \(d_{i-1}\) be the answer on \(i-1\)-th day.
  • \(a_i = ((a_i' - 1 + d_{i-1})\space mod \space N) + 1\)
  • \(b_i = ((b_i' - 1 + d_{i-1})\space mod \space N) + 1\)
  • assume that \(d_0=0\)

Output format:

For every test case output M numbers - maximum safety for each day.

Constraints:

  • \(1 \le T \le 10\)
  • (20 points): \(1 \le N \le 1000, 1 \le M \le 1000\)
  • (30 points): \(1 \le N \le 10^5, 1 \le M \le 10^5\) , \(a_i\) is not in the subtree of \(b_i\).
  • (50 points): \(1 \le N \le 10^5, 1 \le M \le 10^5\).

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