Day 9 part 2

9/9_2.py

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+#!/usr/bin/env python
+# 2021 - Advent Of Code - 9 part 2
+
+def parse_file(file):
+    hmap = []
+    with open(file) as f:
+        for line in f.readlines():
+            linemap = []
+            for n in line.strip():
+                linemap.append(int(n))
+            hmap.append(linemap)
+
+    return hmap
+
+
+def print_hmap(hmap):
+    for y in range(len(hmap)):
+        for x in range(len(hmap[y])):
+            print(hmap[y][x], end='')
+        print()
+
+
+def find_lowpoints(hmap):
+    lpoints = []
+
+    # first line
+    x = 0
+    y = 0
+    if hmap[y][x] < hmap[y][x + 1] and hmap[y][x] < hmap[y + 1][x]:
+        lpoints.append([x, y])
+
+    for x in range(1, len(hmap[y]) - 1):
+        v = hmap[y][x]
+        if v < hmap[y][x - 1] and v < hmap[y][x + 1] and v < hmap[y + 1][x]:
+            lpoints.append([x, y])
+
+    x = len(hmap[y]) - 1
+    if hmap[y][x] < hmap[y][x - 1] and hmap[y][x] < hmap[y + 1][x]:
+        lpoints.append([x, y])
+
+    # middle lines
+    for y in range(1, len(hmap) - 1):
+        x = 0
+        if hmap[y][x] < hmap[y][x + 1] and hmap[y][x] < hmap[y - 1][x] and hmap[y][x] < hmap[y + 1][x]:
+            lpoints.append([x, y])
+
+        for x in range(1, len(hmap[y]) - 1):
+            v = hmap[y][x]
+            if v < hmap[y][x - 1] and v < hmap[y][x + 1] and v < hmap[y - 1][x] and v < hmap[y + 1][x]:
+                lpoints.append([x, y])
+
+        x = len(hmap[y]) - 1
+        if hmap[y][x] < hmap[y][x - 1] and hmap[y][x] < hmap[y - 1][x] and hmap[y][x] < hmap[y + 1][x]:
+            lpoints.append([x, y])
+
+    # last line
+    y = len(hmap) - 1
+    x = 0
+    if hmap[y][x] < hmap[y][x + 1] and hmap[y][x] < hmap[y - 1][x]:
+        lpoints.append([x, y])
+
+    for x in range(1, len(hmap[y]) - 1):
+        v = hmap[y][x]
+        if v < hmap[y][x - 1] and v < hmap[y][x + 1] and v < hmap[y - 1][x]:
+            lpoints.append([x, y])
+
+    x = len(hmap[y]) - 1
+    if hmap[y][x] < hmap[y][x - 1] and hmap[y][x] < hmap[y - 1][x]:
+        lpoints.append([x, y])
+
+    return lpoints
+
+
+def find_basin(hmap, bpoints, point):
+    bpoints.append(point)
+    # print(f'bpoints: {bpoints}')
+    x = point[0]
+    y = point[1]
+
+    # halt if edge, already in list or value is 9
+    # up
+    if y > 0:
+        if hmap[y-1][x] != 9:
+            if [x, y-1] not in bpoints:
+                find_basin(hmap, bpoints, [x, y-1])
+    # down
+    if y < len(hmap) - 1:
+        if hmap[y+1][x] != 9:
+            if [x, y+1] not in bpoints:
+                find_basin(hmap, bpoints, [x, y+1])
+
+    # left
+    if x > 0:
+        if hmap[y][x-1] != 9:
+            if [x-1, y] not in bpoints:
+                find_basin(hmap, bpoints, [x-1, y])
+
+    # right
+    if x < len(hmap[y]) - 1:
+        if hmap[y][x+1] != 9:
+            if [x+1, y] not in bpoints:
+                find_basin(hmap, bpoints, [x+1, y])
+
+    return bpoints
+
+
+# heightmap = parse_file('input_example.txt')
+heightmap = parse_file('input.txt')
+# print_hmap(heightmap)
+low_points = find_lowpoints(heightmap)
+
+risk_levels = 0
+basins = []
+for p in low_points:
+    basins_points = []
+    find_basin(heightmap, basins_points, p)
+    basins.append(basins_points)
+
+
+sizes = [0] * len(basins)
+i = 0
+for b in basins:
+    size = 0
+    for p in b:
+        size += 1
+    sizes[i] = size
+    i += 1
+
+# 3 biggest basins
+biggest_basins = sorted(zip(sizes, basins))[-3:]
+
+product = 1
+for s, b in biggest_basins:
+    print(f'basin size: {s}')
+    product *= s
+
+print(f'product: {product}')