题解 | #逆波兰表达式求值#

注意负数情况的除法

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param tokens string字符串一维数组 
# @return int整型
#
class Solution:
    def evalRPN(self , tokens: List[str]) -> int:
        # write code here
        
        arr = []
        for ele in tokens:
            

            if ele[0] == '-' and len(ele)>1:
                arr.append(0-int(ele[1:]))
            
            elif ele.isdigit():
                arr.append(int(ele))
            
            else:
                
                a1 = arr.pop()
                a2 = arr.pop() 

                if ele == "+":
                    temp = a1 + a2 
                elif ele == "-":
                    temp = a2 - a1
                elif ele == "*":
                    temp = a1 * a2
                elif ele == "/":
                    temp = int(a2/a1) # 负数情况

                arr.append(temp)
                
        return arr[0]