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# 736. Parse Lisp Expression
class Solution(object):
def evaluate(self, expression):
"""
:type expression: str
:rtype: int
"""
stk, d, tokens = [], {}, [""]
def getval(x):
return d.get(x, x)
def evaluate(tokens):
if tokens[0] in ("add", "mult"):
tmp = map(int, map(getval, tokens[1:]))
return str(tmp[0] + tmp[1] if tokens[0] == "add" else tmp[0] * tmp[1])
else:
for i in range(1, len(tokens) - 1, 2):
if tokens[i + 1]:
d[tokens[i]] = getval(tokens[i + 1])
return getval(tokens[-1])
for c in expression:
if c == "(":
if tokens[0] == "let":
evaluate(tokens)
stk.append((tokens, dict(d)))
tokens = [""]
elif c == " ":
tokens.append("")
elif c == ")":
val = evaluate(tokens)
tokens, d = stk.pop()
tokens[-1] += val
else:
tokens[-1] += c
return int(tokens[0])
if __name__ == "__main__":
obj = Solution()
print(obj.evaluate(expression="(let x 2 (mult x (let x 3 y 4 (add x y))))"))
print(obj.evaluate(expression="(let x 3 x 2 x)"))
print(obj.evaluate(expression="(let x 1 y 2 x (add x y) (add x y))"))
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