栈和队列_leetcode150

class Solution(object):
    def evalRPN(self, tokens):
        """
        :type tokens: List[str]
        :rtype: int
        """

        stack = []
        ops = ["+","-","*","/"]

        for i in tokens:
            if i in ops:
                if i == '+':
                    op2 = stack.pop()
                    op1 = stack.pop()
                    num = int(op1) + int(op2)
                    stack.append(num)
                if i == '-':
                    op2 = stack.pop()
                    op1 = stack.pop()
                    num = int(op1) - int(op2)
                    stack.append(num)
                if i == '*':
                    op2 = stack.pop()
                    op1 = stack.pop()
                    num = int(op1) * int(op2)
                    stack.append(num)
                if i == '/':
                    op2 = stack.pop()
                    op1 = stack.pop()
                    num = int(op1) / int(op2)
                    stack.append(num)
            else:
                stack.append(i)

        return stack[0]



class Solution:
    def evalRPN(self, tokens):
        """
        :type tokens: List[str]
        :rtype: int
        """
        stack = list()
        oper = ['+', '-', '*', '/']
        for char in tokens:
            if char not in oper:
                stack.append(int(char))
            else:
                top1 = stack.pop()
                top2 = stack.pop()
                if char == '+':
                    stack.append(top2 + top1)
                elif char == '-':
                    stack.append(top2 - top1)
                elif char == '*':
                    stack.append(top2 * top1)
                elif char == '/':
                    stack.append(int(top2 / top1))
        return stack.pop()



s = Solution()

t = ["2", "1", "+", "3", "*"]
t2 =["10","6","9","3","+","-11","*","/","*","17","+","5","+"]

print s.evalRPN(t2)