LintCode:逆波兰表达式求值

6/(-132)=-1

class Solution:
# @param {string[]} tokens The Reverse Polish Notation
# @return {int} the value
def evalRPN(self, tokens):
# Write your code here
L = []
for elem in tokens:
try:
(int(elem))
L.append(int(elem))
except:
a = L.pop()
b = L.pop()
c = eval(str(b) + elem + str(a))
#python中，正数除负数是向下取整，而C/C++是向零取整
#如在Python中 6/(-132) = -1，而在C/C++中结果是0
#因而对这种情况需要特殊处理
if elem == '/':
if c < 0:
if b % a != 0:
c += 1
L.append(c)
return L[0]