Побег из подземных тоннелей

Очки: 140

Ограничение по времени: 1.0s

Ограничение по памяти: 64M

Автор:

montes332

Problem types

Allowed languages

C++, Python

Дана карта подземного рудника в виде прямоугольной сетки из камер. Каждая камера может быть либо проходимой, либо заваленной породой.

Символ '.' обозначает свободную камеру, по которой можно пройти.
Символ '+' обозначает заваленную камеру, пройти через неё нельзя.

Шахтёр начинает в заданной свободной камере entrance = [entrancerow, entrancecol].

За один шаг он может перейти из текущей камеры в соседнюю по стороне: вверх, вниз, влево или вправо, если эта камера находится в пределах карты и не завалена.

Выходом из подземных тоннелей считается любая свободная камера, расположенная на границе карты, кроме стартовой камеры, даже если стартовая камера тоже лежит на границе.

Требуется определить минимальное число шагов, необходимое шахтёру, чтобы добраться до ближайшего выхода. Если выбраться невозможно, выведите -1.

Входные данные

Вход состоит из следующих данных:

два целых числа m и n — количество строк и столбцов карты;
m строк длины n, описывающих карту рудника;
два целых числа entrancerow и entrancecol — координаты стартовой камеры.

Гарантируется, что стартовая камера является свободной.

Выходные данные

Выведите одно целое число — минимальное количество шагов до ближайшего выхода из тоннелей, либо -1, если такого пути не существует.

Ограничения

1 <= m, n <= 100
maze[i][j] равно либо '.', либо '+'
0 <= entrancerow < m
0 <= entrancecol < n
maze[entrancerow][entrancecol] == '.'

Примеры

Пример 1

Входные данные

2 100
....................................................................................................
....................................................................................................
0 50

Выходные данные

Пример 2

Входные данные

100 100
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50 50

Выходные данные

-1