ZOJ Problem Set - 1142
By filling a rectangle with slashes (/) and backslashes (\), you can generate nice little mazes. Here is an example:
As you can see, paths in the maze cannot branch, so the whole maze only contains cyclic paths and paths entering somewhere and leaving somewhere else. We are only interested in the cycles. In our example, there are two of them.
Your task is to write a program that counts the cycles and finds the length of the longest one. The length is defined as the number of small squares the cycle consists of (the ones bordered by gray lines in the picture). In this example, the long cycle has length 16 and the short one length 4.
The input is terminated by a test case beginning with w = h = 0. This case should not be processed.
Output a blank line after each test case.
Source: Mid-Central European Regional Contest 1999