day 9
you can find the description here and you can find the code here
for part one, simply count the number of cells in which all neighbors are strictly greater.
for part two, floodfill until you have previously visited or until you find a height 9
def floodfill(grid, r, c):
if grid[r][c] is None or grid[r][c] == 9:
return 0
s, grid[r][c] = 1, None
for nr, nc in neighbors(grid, r, c):
s += floodfill(grid, nr, nc)
return s