题目:
题解:
func calculate(s string) (ans int) {
stack := []int{}
preSign := '+'
num := 0
for i, ch := range s {
isDigit := '0' <= ch && ch <= '9'
if isDigit {
num = num*10 + int(ch-'0')
}
if !isDigit && ch != ' ' || i == len(s)-1 {
switch preSign {
case '+':
stack = append(stack, num)
case '-':
stack = append(stack, -num)
case '*':
stack[len(stack)-1] *= num
default:
stack[len(stack)-1] /= num
}
preSign = ch
num = 0
}
}
for _, v := range stack {
ans += v
}
return
}