codeforces 329B B. Biridian Forest 精巧的bfs

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你是一位 mikemon 养殖者，必须穿越 Biridian Forest。森林由 r 行 c 列构成，有树的格子不能进入。你的目标是离开森林，但与其他养殖者相遇会引发战斗。你需要制定一个最小化战斗次数的移动序列并发布到博客。题目提供森林地图，你需要找出从起点到出口的路径，途中遇到的养殖者将尽可能与你战斗。任务是找到使战斗次数最少的移动序列，并输出该战斗次数。

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You're a mikemon breeder currently in the middle of your journey to become a mikemon master. Your current obstacle is go through the infamous Biridian Forest.

The forest

The Biridian Forest is a two-dimensional grid consisting of r rows and c columns. Each cell in Biridian Forest may contain a tree, or may be vacant. A vacant cell may be occupied by zero or more mikemon breeders (there may also be breeders other than you in the forest). Mikemon breeders (including you) cannot enter cells with trees. One of the cells is designated as the exit cell.

The initial grid, including your initial position, the exit cell, and the initial positions of all other breeders, will be given to you. Here's an example of such grid (from the first example):

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Moves

Breeders (including you) may move in the forest. In a single move, breeders may perform one of the following actions:

Do nothing.
Move from the current cell to one of the four adjacent cells (two cells are adjacent if they share a side). Note that breeders cannot enter cells with trees.
If you are located on the exit cell, you may leave the forest. Only you can perform this move — all other mikemon breeders will never leave the forest by