Merge pull request #99 from MaritimeOptima/day1819/preng

Day 18 and 19 solutions in python by preng. Very low-level code, avoiding higher level python temptations as a re-learning excercise

Author: Arxcis

days/day-18/io/preng.input

@@ -0,0 +1,2 @@
+6640667297513
+451589894841552

days/day-18/io/preng.output

@@ -0,0 +1,130 @@
+from functools import reduce
+from sys import stdin
+import math
+import re
+
+# Long winded code that does not use high-level system libraries
+
+def get_stdin():
+    return [line.rstrip() for line in stdin]
+
+def parentokens(tokens):
+    closecnt = 0
+    for i in range(len(tokens)):
+        t = tokens[i]
+        if t == "(":
+            closecnt -= 1
+        elif t == ")":
+            closecnt += 1
+            if closecnt == 1:
+                return tokens[0:i], tokens[i+1:]
+    print("unbalanced", tokens)
+
+def tokenize(expr):
+    tokens = []
+    pos = 0
+    while pos < len(expr):
+        c = expr[pos]
+        if c == " ":
+            pos += 1
+        elif c == "(":
+            tokens.append(c)
+            pos += 1
+        elif c == ")":
+            tokens.append(c)
+            pos += 1
+        elif c == "+":
+            tokens.append(sum)
+            pos += 1
+        elif c == "*":
+            tokens.append(math.prod)
+            pos += 1
+        else:
+            token = re.findall(r'-{0,1}\d+', expr[pos:])[0]
+            tokens.append(int(token))
+            pos += len(token)
+    return tokens      
+
+def presedence(a, b):
+    return a == sum and b == math.prod
+
+def parsenext(tokens, builder):
+    if len(tokens) == 1:
+        return tokens[0], []
+    t = tokens.pop(0)
+    if t == "(":
+        inside, tail = parentokens(tokens)
+        return parsetree(inside, builder), tail
+    else:
+        return parsetree([t], builder), tokens
+
+def parsetree(tokens, builder, left = None):
+    op = None
+    right = None
+    if len(tokens) == 1:
+        return Expr(None, tokens[0], None)
+    if left is None:
+        left, tokens = parsenext(tokens, builder)
+    if len(tokens) == 0:
+        return Expr(None, left, None)
+    op = tokens.pop(0)
+    right, tokens = parsenext(tokens, builder)
+    if len(tokens) == 0:
+        return Expr(op, left, right)
+    return builder(op, left, right, tokens)
+
+def part1builder(op, left, right, tail):
+    return parsetree(tail, part1builder, Expr(op, Expr(None,left,None), Expr(None,right,None)))
+
+def part2builder(op, left, right, tail):
+    if presedence(tail[0], op):
+        op2 = tail[0]
+        nexttoken, tail = parsenext(tail[1:], part2builder)
+        return Expr(op, left, parsetree(tail, part2builder, Expr(op2, right, nexttoken)))
+    else:
+        return parsetree(tail, part2builder, Expr(op, Expr(None,left,None), Expr(None,right,None)))
+
+class Expr:
+    def __init__(self, op, left, right):
+        self.op = op
+        self.left = left
+        self.right = right
+
+    def isplus(self):
+        return self.op is not None and self.op == sum
+
+    def ismult(self):
+        return self.op is not None and self.op == math.prod
+
+    def calc(self):
+        if self.isplus():
+            return self.value(self.left) + self.value(self.right)
+        elif self.ismult():
+            return self.value(self.left) * self.value(self.right)
+        else:
+            return self.value(self.left)
+
+    def value(self, node):
+        if isinstance(node, Expr):
+            return node.calc()
+        else:
+            return node
+    
+    def __str__(self):
+        if self.op is None:
+            return "%s" % (self.left)
+        if self.isplus():
+            return "(%s + %s) " % (self.left, self.right)
+        else:
+            return "(%s * %s) " % (self.left, self.right)
+
+    def __repr__(self):
+        return self.__str__()
+
+
+# PART 1
+lines = get_stdin()
+print(sum([parsetree(tokenize(l), part1builder).calc() for l in lines]))
+
+# PART 2
+print(sum([parsetree(tokenize(l), part2builder).calc() for l in lines]))

days/day-18/solutions/day18.preng.py

@@ -3,10 +3,8 @@ set -euo pipefail
 
 D=$(dirname $(realpath $0))
 
-echo "--- Day 18: --- ????? --- ❌"
+echo "--- Day 18: --- Operation Order ---"
 #$D/../../lang/go.sh     "$D/solutions/*.go"  "$D/io/*"
 #$D/../../lang/sml.sh    "$D/solutions/*.sml" "$D/io/*"
-#$D/../../lang/python.sh "$D/solutions/*.py"  "$D/io/*"
+$D/../../lang/python.sh "$D/solutions/*.py"  "$D/io/*"
 #$D/../../lang/deno.sh   "$D/solutions/*.ts"  "$D/io/*"
-
-exit 1337;