# Why my codes cannot pass all the test cases?

• ``````class Solution(object):
def calculate(self, s):
"""
:type s: str
:rtype: int
"""
number,op = [],[]
tmp = ''
for i in range(len(s)):

if s[i].isdigit():
tmp+=s[i]
if i == len(s)-1 or not s[i+1].isdigit():
number.append(int(tmp))
print number
tmp = ''
elif s[i] in '(+-':
op.append(s[i])
elif s[i] == ')':
while op[-1]!='(':
self.compute(number,op)
op.pop()
while op:
self.compute(number,op)
return number[-1]

def compute(self,number,op):
a,b = number.pop(),number.pop()
opr = op.pop()
if opr == '+':
number.append(a+b)
if opr == '-':
number.append(b-a)``````

• Slight modification to your code which works fine. Please check the below code:

``````def compute(self, num, op):
a, b=num.pop(), num.pop()
l=len(op)
asign=op.pop()
if l==1 or op[-1]=="(":
if asign=="+":
num.append(a+b)
elif asign=="-":
num.append(b-a)
return

bsign= op.pop()
if asign == bsign:
num.append(a+b)
op.append(asign)
elif asign!=bsign:
if a > b:
num.append(a-b)
op.append(asign)
elif b > a:
num.append(b-a)
op.append(bsign)

def calculate(self, s):
"""
:type s: str
:rtype: int
"""
num, op=[],[]
n=len(s)
tmp=""
for i in range(n):
if s[i].isdigit():
tmp+=s[i]
if i==n-1 or not s[i+1].isdigit():
num.append(int(tmp))
tmp=""
elif s[i] in "(+-":
op.append(s[i])
elif s[i]==")":
while op[-1]!="(":
self.compute(num,op)
op.pop()

while op:
self.compute(num, op)

return num[-1]``````

• Could you please explain the compute() function?

• Basically, your compute function had problem in calculating case like 7 -3+2, in this case your compute function contains 7-5=2, but actually you need to take care of the integer sign also, so it should compute 7-1=6. That is why you need to take asign and bsign, and compute the result accordingly and store the sign again back to op list.

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