[Problem D | 1995 East-Central problem set | My ACM problem archive | my home page]

ACM International Collegiate programming Contest

A digital image is composed of the two characters, "X" and " " (space). There are always 25 columns to an
image, but the number of rows, *N*, is variable. Column one (1) will always have an "X" in it and will be
part of the left surface. The left surface can extend to the right from column one (1) as contiguous X's.
Similarly, column 25 will always have an "X" in it and will be part of the right surface. The right surface
can extend to the left from column 25 as contiguous X's.

Digital-Image View of Surfaces |
---|

Left Right XXXX XXXXX <-- 1 XXX XXXXXXX XXXXX XXXX XX XXXXXX . . . . . . XXXX XXXX XXX XXXXXX <-- N | | 1 25 |

Foreach image given, you are to determine the total "void" that will exist after the left surface has been brought into contact with the right surface. The "void" is the total count of the spaces that remains between the left and right surfaces after they have been brought into contact.

The two surfaces are brought into contact by displacing them strictly horizontally towards each other until a rightmost "X" of the left surface of some row is immediately to the left of the leftmost "X" of the right surface of that row. There is no rotation or twisting of these two surfaces as they are brought into contact; they remain rigid, and only move horizontally.

Note: The original image may show the two surfaces already in contact, in which case no displacement enters into the contact roughness estimation.

First line -- A single unsigned integer,The end of data is signaled by a null data set having a zero on the first line of an image data set and no further data.N, with value greater than zero (0) and less than 13. The first digit ofNwill be the first character on a line.Next

Nlines -- Each line has exactly 25 characters; one or more X's, then zero or more spaces, then one or more X's.

## Sample Input4 XXXX XXXXX XXX XXXXXXX XXXXX XXXX XX XXXXXX 2 XXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXX 1 XXXXXXXXX XX 0 |
## Output for the Sample Input4 0 0 |

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Last updated November 6, 1997