You have an integer matrix representing a plot of land, where the value at that location represents the height above sea level. A value of zero indicates water. A pond is a region of water connected vertically, horizontally, or diagonally. The size of the pond is the total number of connected water cells. Write a method to compute the sizes of all ponds in the matrix.
Example:
Input: [ [0,2,1,0], [0,1,0,1], [1,1,0,1], [0,1,0,1] ] Output: [1,2,4]
Note:
0 < len(land) <= 10000 < len(land[i]) <= 1000