- Time limit: 1.00 s
- Memory limit: 512 MB
You are playing a game consisting of n planets. Each planet has a teleporter to another planet (or the planet itself).
You have to process q queries of the form: You are now on planet a and want to reach planet b. What is the minimum number of teleportations?
The first input line contains two integers n and q: the number of planets and queries. The planets are numbered 1,2,\ldots,n.
The second line contains n integers t_1,t_2,\ldots,t_n: for each planet, the destination of the teleporter.
Finally, there are q lines describing the queries. Each line has two integers a and b: you are now on planet a and want to reach planet b.
For each query, print the minimum number of teleportations. If it is not possible to reach the destination, print -1.
- 1 \le n, q \le 2 \cdot 10^5
- 1 \le a,b \le n
5 3 2 3 2 3 2 1 2 1 3 1 4
1 2 -1