The challenge
The shortest code by character count to identify and mark water depressions in the ASCII representation of a land from input.
Input will be an ASCII representation of a landscape, having hills, valleys and flat lands. The program should simulate what the landscape would look like if if was flooded - filling all valleys with water (character x).
The landscape will always start and stop with the character _ and will be at least 2 characters long, making the shortest input __.
A hill is defined as a raise, and should not be filled with water:
__
_/ \_
A valley is defined as a depression and will be filled with water until a flatland is encountered:
_ _
\__/
Input can be assumed clean and will be composed only from the characters space (), newline (\n), underscore (_), and forward and backward slashes (/ and \). Input can be seen as a continuous line, and any input that contains ambiguous line input such as _/_ or
_ _
\_/
/ \
Is considered invalid.
Regarding underwater caves, water level should be maintained if cave level goes above water level.
Test cases
Input:
__/\__
\__
\ ___ ___________
/ / \_ \_
\_____/ \__ _/
\/
Output:
__/\__
\__
\ ___ ___________
/xxxxxx/ \xxxxxx\_
\xxxxx/ \xxxxx/
\/
Input:
__ ___
/ \_____/
/ _______
________ / \ /
_____/ \ /__ \ \_
____ / \ /__/ __/
\_ / \ ____/
\______\ /____/
Output:
__ ___
/ \xxxxx/
/ _______
________ / \ /
_____/ \xxx/__ \xxxx\_
____ / \xxxx/__/xxxxx/
\xxxxxxxx/ \xxxxxxxxx/
\xxxxxx\ /xxxx/
Input:
__ _
_ ____ ____ _____/ \ /
\ / \ __________/ \ __/ ___ /___\
\___/ \ \ \ \___/ /_
/________\ \___________\
Output:
__ _
_ ____ ____ _____/ \xxx/
\xxxxx/ \xxxxxxxxxxxxxxxxxx/ \xxxxxx/ ___ /xxx\
\xxx/ \xxxxxxx\ \xxx\___/xx/_
/xxxxxxxx\ \xxxxxxxxxxx\
Code count includes input/output (i.e full program).