2020 day 18

2020/d18.py

@@ -0,0 +1,106 @@
+from lib import get_data
+
+
+def eval_1(s) -> int:
+    if type(s) is int:
+        return s
+    i = 0
+    parts = []
+    while i < len(s):
+        if s[i] == "(":
+            nested = 1
+            r = "("
+            i += 1
+            while nested > 0:
+                r += s[i]
+                if s[i] == ")":
+                    nested -= 1
+                elif s[i] == "(":
+                    nested += 1
+                i += 1
+            parts.append(r[1:-1])
+        elif s[i].isdigit():
+            d = ""
+            while i < len(s) and s[i].isdigit():
+                d += s[i]
+                i += 1
+            parts.append(int(d))
+        elif s[i] == " ":
+            pass
+        elif s[i] == "*" or s[i] == "+":
+            parts.append(s[i])
+        i += 1
+
+    i = 0
+    while len(parts) > 1:
+        if parts[1] == "*":
+            parts[2] = eval_1(parts[0]) * eval_1(parts[2])
+            parts = parts[2:]
+        elif parts[1] == "+":
+            parts[2] = eval_1(parts[0]) + eval_1(parts[2])
+            parts = parts[2:]
+        else:
+            assert False
+    return parts[-1]
+
+
+def eval_2(s) -> int:
+    if type(s) is int:
+        return s
+    i = 0
+    parts = []
+    while i < len(s):
+        if s[i] == "(":
+            nested = 1
+            r = "("
+            i += 1
+            while nested > 0:
+                r += s[i]
+                if s[i] == ")":
+                    nested -= 1
+                elif s[i] == "(":
+                    nested += 1
+                i += 1
+            parts.append(r[1:-1])
+        elif s[i].isdigit():
+            d = ""
+            while i < len(s) and s[i].isdigit():
+                d += s[i]
+                i += 1
+            parts.append(int(d))
+        elif s[i] == " ":
+            pass
+        elif s[i] == "*" or s[i] == "+":
+            parts.append(s[i])
+        i += 1
+
+    while len(parts) > 1:
+        new_parts = []
+        for i in range(0, len(parts) - 1, 2):
+            if parts[i + 1] == "+":
+                new_parts.append(eval_2(parts[i]) + eval_2(parts[i + 2]))
+                new_parts += parts[i + 3 :]
+                break
+            elif parts[1] == "*":
+                new_parts.append(parts[i])
+                new_parts.append(parts[i + 1])
+            else:
+                assert False
+        else:
+            assert parts[1] == "*"
+            new_parts = [eval_2(parts[0]) * eval_2(parts[2])]
+            new_parts += parts[3:]
+        parts = new_parts
+    return parts[-1]
+
+
+data = get_data(__file__)
+
+t1, t2 = 0, 0
+for line in data.splitlines():
+    t1 += eval_1(line)
+    t2 += eval_2(line)
+
+print(t1)
+print(t2)
+assert t2 == 290726428573651

README.md

@@ -156,7 +156,8 @@ Solutions and utility script for Advent of Code challenges in Python.
 - Day 15: 17:57 (Too slow for an easy one like this)
 - Day 16: 33:00 (Not too unhappy really.)
 - Day 17: 10:00 (40th)
-- Day 18:
+- Day 18: 80:00 (I am struggling with stuff where parsing is involved)
+- Day 19:
 
 ## AoC 2022