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# SunnyDisposish/rainwater.py

Created March 26, 2020 06:37
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 def max_to_left(elevations): max_so_far = float(inf) * -1 maxes_to_left = [] for h in elevations: if h > max_so_far: max_so_far = h maxes_to_left.append(max_so_far) return maxes_to_left def max_to_right(elevations): max_so_far = float(inf) * -1 maxes_to_right = [] for h in reversed(elevations): if h > max_so_far: max_so_far = h maxes_to_right.append(max_so_far) return maxes_to_right def depth(elevations, max_to_right, max_to_left): depths = [] for h, i in enumerate(elevations): depth_here = max(0, min(max_to_right[i], max_to_left[i])-h) depths.append(depth_here) return depths class Lake(object): def __init__(self, lake_array, start, end): self.lake_array = lake_array, self.start = start self.end = end self.volume = sum(lake_array) def find_lake_boundaries(depths): starts = [] ends = [] for (left, i), (right, j) in zip(enumerate(depths[:-1]), enumerate(depths[1:])): if (left == 0 or i == 0) and right != 0: starts.append(j) if left != 0 and (right == 0 or right == len(depths)): ends.append(j) return zip(starts, ends) def make_lakes(depths): boundaries = find_lake_boundaries(depths) lakes = [] for start, end in boundaries: lakes.append(Lake(depths[start:end], start, end)) return lakes def best_lake(elevations): depths = depths(elevations, maxes_to_left(elevations), max_to_right(elevations)) lakes = make_lakes(depths) best_lake = max(lake.volume for lake in lakes) return (best_lake.start, best_lake.end)