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| func calculate(s string) int {
stack := make([]int, 0)
num := 0
sign := 1
result := 0
for i := 0; i < len(s); i++ {
if isDigit(s[i]) {
num = num*10 + int(s[i]-'0')
} else if s[i] == '+' {
result += sign * num
num = 0
sign = 1
} else if s[i] == '-' {
result += sign * num
num = 0
sign = -1
} else if s[i] == '(' {
stack = append(stack, result)
stack = append(stack, sign)
result = 0
sign = 1
} else if s[i] == ')' {
result += sign * num
num = 0
result *= stack[len(stack)-1]
result += stack[len(stack)-2]
stack = stack[:len(stack)-2]
}
}
return result + sign*num
}
func isDigit(ch byte) bool {
return ch >= '0' && ch <= '9'
}
|