P6705 [COCI 2010/2011 #7] POŠTAR

Mirko got a job as a postman in a small mountain town. The town can be represented as an $n \times n$ matrix. Each cell has one of three types: a house marked with `K`, a post office marked with `P`, or a pasture marked with `.`. In addition, each cell is assigned a height. Every morning, Mirko delivers mail to every house in the town. He starts from the cell marked `P`. Mirko can move to an adjacent cell horizontally, vertically, or diagonally. After delivering the last letter, he must return to the post office. Mirko does not know how boring his job will be. Let Mirko’s fatigue be the difference between the maximum and minimum heights among all cells he visits while delivering the mail. Help him find a way to deliver all the mail with the minimum possible fatigue.

You are given an $n \times n$ matrix. Each position may be one of `K`, `P`, `.`. It also has a height $h_{i,j}$. You need to start from the position marked `P`, move horizontally, vertically, or diagonally, visit all positions marked `K`, and finally return to the starting position. Along this route, you need to minimize $max_h - min_h$ over all visited positions. Output this minimum value.

The first line contains an integer $n$. The next $n$ lines each contain $n$ characters describing the matrix. The next $n$ lines each contain $n$ positive integers, representing the heights of the cells.

Output a non-negative integer, the minimum fatigue.

#### Explanation of Sample 1 Starting from the post office, Mirko can move directly to the house and then return to the post office. Since the two cells have the same height, Mirko’s fatigue is $0$. #### Constraints In the matrix, `P` appears exactly once, and `K` appears at least once. For $100\%$ of the testdata, $2 \le n \le 50$. #### Notes This problem is worth $100$ points. Translated from [COCI2010-2011](https://hsin.hr/coci/archive/2010_2011/) [CONTEST #7](https://hsin.hr/coci/archive/2010_2011/contest7_tasks.pdf) T4 POŠTAR. Translated by ChatGPT 5