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operators = {
'*': 1,
'+': 0,
}
def tokenize(xs):
result = []
i = 0
while i < len(xs):
current = xs[i]
if current in operators.keys():
result.append(current)
i += 1
continue
else:
i += 1
while i < len(xs) and xs[i] in {str(n) for n in range(10)}:
current += xs[i]
i += 1
result.append(int(current))
return result
def postfix(xs):
result = []
s = []
for x in xs:
if x in operators.keys():
while s and operators[s[-1]] >= operators[x]:
result.append(s.pop())
s.append(x)
else:
result.append(x)
while s:
result.append(s.pop())
return result
def evaluate(xs):
s = []
for x in xs:
print(s, x)
if x == '*':
s.append(s.pop() * s.pop())
elif x == '+':
s.append(s.pop() + s.pop())
else:
s.append(x)
print(s)
return s[-1]
print(evaluate(postfix(tokenize("12+3*10"))))
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