class Solution:
def evalRPN(self, tokens: List[str]) -> int:
f1 = lambda x,y:x+y
f2 = lambda x,y:x-y
f3 = lambda x,y:x*y
f4 = lambda x,y:int(x/y)
dic = {'+':f1,'-':f2,'*':f3,'/':f4}
stack = []
for i in tokens:
if i in dic:
x, y = stack.pop(),stack.pop()
stack.append(dic[i](y,x))
else:
stack.append(int(i))
print(stack)
return stack[-1]
- 题目分析
- 给定一个字符数字组,里面含有加减乘除
- 预先用lambda定义4个函数,并根据运算符号映射到hash表中
- 如果是数字直接入栈,如果不是数字那就出栈进行计算,然后再将计算的结果进行入栈操作