Day 10

2021/day10.py

@@ -0,0 +1,37 @@
+import sys
+
+
+CHARMAP = {"]": "[", ")": "(", "}": "{", ">": "<"}
+SCOREMAP = {")": 3, "]": 57, "}": 1197, ">": 25137}
+SCOREMAP2 = {"(": 1, "[": 2, "{": 3, "<": 4}
+
+
+def main():
+    lines = [line.rstrip() for line in sys.stdin]
+    error_score = 0
+    comp_scores = []
+    for line in lines:
+        corrupted = None
+        state = []
+        for char in line:
+            if char in CHARMAP:
+                if state and state[-1] == CHARMAP[char]:
+                    state.pop()
+                else:
+                    corrupted = char
+                    break
+            else:
+                state.append(char)
+        if corrupted:
+            error_score += SCOREMAP[corrupted]
+        else:
+            cs = 0
+            for char in reversed(state):
+                cs = cs * 5 + SCOREMAP2[char]
+            comp_scores.append(cs)
+    print(error_score)
+    print(list(sorted(comp_scores))[len(comp_scores) // 2])
+
+
+if __name__ == "__main__":
+    main()

2021/day9.py

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+import sys
+
+
+def main():
+    lines = [line.rstrip() for line in sys.stdin]
+    nc = len(lines[0])
+    nr = len(lines)
+    m = [list(map(int, line)) for line in lines]
+
+    # Part 1
+    low_points = []
+    rlevels = 0
+    for x, row in enumerate(m):
+        for y, val in enumerate(row):
+            if (
+                (x == 0 or m[x - 1][y] > val)
+                and (x == nr - 1 or m[x + 1][y] > val)
+                and (y == 0 or m[x][y - 1] > val)
+                and (y == nc - 1 or m[x][y + 1] > val)
+            ):
+                low_points.append((x, y))  # for part 2
+                rlevels += val + 1
+    print(rlevels)
+
+    # Part 2
+    basins = [expand_basin(m, (x, y), nc, nr) for x, y in low_points]
+    a, b, c = sorted(map(len, basins))[-3:]
+    print(a * b * c)
+
+
+def expand_basin(m, start, nc, nr):
+    basin = []
+    sx, sy = start
+    explo = [(sx, sy)]
+    while explo:
+        pos = explo.pop(0)
+        x, y = pos
+        if m[x][y] == 9:
+            continue
+        basin.append(pos)
+        if x > 0 and (n := (x - 1, y)) not in basin and n not in explo:
+            explo.append(n)
+        if x < nr - 1 and (n := (x + 1, y)) not in basin and n not in explo:
+            explo.append(n)
+        if y > 0 and (n := (x, y - 1)) not in basin and n not in explo:
+            explo.append(n)
+        if y < nc - 1 and (n := (x, y + 1)) not in basin and n not in explo:
+            explo.append(n)
+    return basin
+
+
+if __name__ == "__main__":
+    main()