leetcode——150. 逆波兰表达式求值

class Solution(object):
    def evalRPN(self, tokens):
        """
        :type tokens: List[str]
        :rtype: int
        """
        stack=[]
        for i in tokens:
            if i not in ‘+-*/‘:
                stack.append(i)
            else:
                a=stack.pop()
                b=stack.pop()
                if i==‘+‘:
                    c=int(a)+int(b)
                    stack.append(c)
                if i==‘-‘:
                    c = int(b) - int(a)
                    stack.append(c)
                if i==‘*‘:
                    c = int(a) * int(b)
                    stack.append(c)
                if i==‘/‘:
                    c = int(b) / int(a)
                    if int(a)*int(b)<0 and int(b)!=c*int(a):
                        c=c+1
                    stack.append(c)
        return stack.pop()