Day 3

2023/day03/code.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python3
+
+import sys
+
+NUMS = ['0','1','2','3','4','5','6','7','8','9']
+
+
+def get_number(schema, x, y):
+    start = x
+    while start > 0:
+        if schema[y][start-1] in NUMS: start -= 1
+        else: break
+    num = ''
+    while start < len(schema[y]) and schema[y][start] in NUMS:
+        num += schema[y][start]
+        start += 1
+    return int(num), start
+
+
+def part_number(schema, x, y):
+    for i in [max(0,x-1), x, min(x+1, len(schema[x])-1)]:
+        for j in [max(0,y-1), y, min(y+1, len(schema)-1)]:
+            if not (schema[j][i] in NUMS or schema[j][i] == '.'):
+                return get_number(schema, x, y)
+    return 0, x+1
+
+
+def gear_ratio(schema, x, y):
+    parts = [0,0]
+    for j in [max(0,y-1), y, min(y+1, len(schema)-1)]:
+        next_x = 0
+        for i in [max(0,x-1), x, min(x+1, len(schema[x])-1)]:
+            if i < next_x: continue
+            if schema[j][i] in NUMS:
+                if parts[0] == 0: parts[0], next_x = get_number(schema, i, j)
+                else: parts[1], next_x = get_number(schema, i, j)
+    return parts[0] * parts[1]
+
+
+if __name__ == '__main__':
+    schema = [list(line.strip('\n')) for line in open(sys.argv[1])]
+
+    # challenge 1
+    res1 = 0
+    for y, line in enumerate(schema):
+        next_x = 0
+        for x, sym in enumerate(line):
+            if x < next_x: continue
+            if sym in NUMS:
+                n, next_x = part_number(schema, x, y)
+                res1 += n
+
+    res1 = str(res1)
+    print(f"challenge 1:\n{res1}\n")
+
+    # challenge 2
+    res2 = 0
+    for y, line in enumerate(schema):
+        for x, sym in enumerate(line):
+            if sym == '*': res2 += gear_ratio(schema, x, y)
+    res2 = str(res2)
+    print(f"challenge 2:\n{res2}\n")
+