1106. parsing a boolean expression

A boolean expression is an expression that evaluates to either true or false. It can be in one of the following shapes:

• 't' that evaluates to true.
• 'f' that evaluates to false.
• '!(subExpr)' that evaluates to the logical NOT of the inner expression subExpr.
• '&(subExpr1, subExpr2, ..., subExprn)' that evaluates to the logical AND of the inner expressions subExpr1, subExpr2, ..., subExprn where n >= 1.
• '|(subExpr1, subExpr2, ..., subExprn)' that evaluates to the logical OR of the inner expressions subExpr1, subExpr2, ..., subExprn where n >= 1.

Given a string expression that represents a boolean expression, return the evaluation of that expression.

It is guaranteed that the given expression is valid and follows the given rules.

solution

Very similar to 224-basic-calculator.

def parseBoolExpr(self, expression: str) -> bool:
	def eval_op(bools, op):
		if op == "!":
			return not bools[0]
		elif op == "&":
			return all([b for b in bools])
		elif op == "|":
			return any([b for b in bools])
	  
	def parse(idx) -> tuple[list[bool], int]:
		i = idx
		bools = []
		op = None
	  
		while i < len(expression):
			c = expression[i]
		  
			if c == "t":
				bools.append(True)
				i += 1
			elif c == "f":
				bools.append(False)
				i += 1
			elif c in {"|", "!", "&"}:
				op = c
				i += 1
			elif c == "(":
				inner_bools, next_idx = parse(i+1)
				bools.append(eval_op(inner_bools, op))
				i = next_idx
				op = None
			elif c == ")":
				return bools, i+1
			else:
				i += 1
	  
		return bools, i
	  
	return parse(0)[0][0]