A river can flow either downhill, or at a level elevation for a certain distance. Given a topographical map (a map representing elevations) and a maximum level flow distance, write a method to determine the largest area that a river can cover, if it starts at any location on the map.
The map will be a String[] representing the elevations of each coordinate, with each elevation being a single digit number between 0 (lowest) and 9 (highest).
The maximum level flow distance, maxDist, will be the longest a river can travel on level ground. So if the distance is 0, a river must flow downhill. If the distance is 1, it can flow to 1 adjacent coordinate of the same altitude, in each direction, before it must flow downhill. If the distance is 2, immediately after flowing downhill (or from the starting point), the river can flow to any adjacent coordinate of the same altitude, and then once again to any coordinate adjacent to the new one and of the same altitude, before it must go down hill. For this calculation, the river flows in the 4 primary directions (north, south, east, and west). Notice that since a river will go in any direction it can, it's more of a "flood" than a "river". Thus when determining the area covered by a river starting at a certain point, you must find the area of all the points that can be reached following the above constraints.
For example:
0000000000
0111111110
0122222210
0123333210
0123443210
0123443210
0123333210
0122222210
0111111110
0000000000
Represents a peak with an elevation of 4.
If maxDist = 2 and the river starts flowing at the '*' then the river can cover an area of 16, shown by '~'.
~~~~~~~000
~~*~~11110
~~22222210
~123333210
~123443210
0123443210
0123333210
0122222210
0111111110
0000000000
However this isn't the largest area. If the river starts flowing at the peak, then the river can cover the entire area of 100.
