#P15502. [ICPC 2025 APC] Book Sorting

[ICPC 2025 APC] Book Sorting

Description

You have nn books arranged from left to right on a bookshelf. These books are uniquely labeled from 11 to nn. The ii-th book from the left is labeled pip_i. You want to sort the books so that their labels are in ascending order from left to right. In one step, you can perform one of the following actions:

  • Choose two adjacent books and swap them.
  • Choose one book and move it to the leftmost position.
  • Choose one book and move it to the rightmost position.

Compute the minimum number of steps required to sort the books.

Input Format

The first line of input contains an integer nn (2n5000002 \leq n \leq 500\,000). The second line contains nn pairwise distinct integers p1,p2,,pnp_1, p_2, \ldots, p_n (1pin1 \leq p_i \leq n).

Output Format

Output the minimum number of steps to sort the books in ascending order from left to right by their labels.

6
6 2 1 4 3 5
3
9
9 2 4 3 7 5 1 8 6
5

Hint

Explanation for the sample input/output #1

You can do the following three steps in order: swap the books labeled 22 and 11, swap the books labeled 44 and 33, and move the book labeled 66 to the rightmost position.

$\begin{aligned}6 \ 2 \ 1 \ 4 \ 3 \ 5 &\rightarrow 6 \ \mathbf{1} \ \mathbf{2} \ 4 \ 3 \ 5 \\&\rightarrow 6 \ 1 \ 2 \ \mathbf{3} \ \mathbf{4} \ 5 \\&\rightarrow 1 \ 2 \ 3 \ 4 \ 5 \ \mathbf{6}\end{aligned}$

It can be shown that two or fewer steps are insufficient to sort the books.