2020: d18: ex2: add solution

This commit is contained in:
Bruno BELANYI 2020-12-18 10:10:08 +01:00
parent 9d2ad5dce4
commit b2b051837f

79
2020/d18/ex2/ex2.py Executable file
View file

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#!/usr/bin/env python
import sys
from typing import Callable, Dict, List
"""
E : T [ * T ]*
T : G [ + G ]*
G : '(' E ')' | CONSTANT
"""
def parse_g(expr: List[str]) -> int:
top = expr.pop(0)
if top == "(":
ans = parse_e(expr)
assert expr.pop(0) == ")"
return ans
return int(top)
def parse_t(expr: List[str]) -> int:
lhs = parse_g(expr)
while len(expr) and expr[0] == "+":
expr.pop(0)
rhs = parse_g(expr)
lhs += rhs
return lhs
def parse_e(expr: List[str]) -> int:
lhs = parse_t(expr)
while len(expr) and expr[0] == "*":
expr.pop(0)
rhs = parse_t(expr)
lhs *= rhs
return lhs
def parse_infix(input: List[str]) -> int:
"""
Parses the given string in infix notation.
"""
ans = parse_e(input)
assert len(input) == 0
return ans
def tokenize(expr: str) -> List[str]:
res = []
def split_tok(tok: str) -> None:
if "(" not in tok and ")" not in tok:
res.append(tok)
if "(" in tok:
res.append("(")
split_tok(tok[1:])
if ")" in tok:
split_tok(tok[:-1])
res.append(")")
for tok in expr.split():
split_tok(tok)
return res
def solve(raw: List[str]) -> int:
return sum(parse_infix(tokenize(expr)) for expr in raw)
def main() -> None:
input = [line.strip() for line in sys.stdin.readlines()]
print(solve(input))
if __name__ == "__main__":
main()