我要招人

去企业版

首页 > 试题广场 >

逆波兰表达式求值

[编程题]逆波兰表达式求值

热度指数：21923 时间限制：C/C++ 1秒，其他语言2秒空间限制：C/C++ 256M，其他语言512M
算法知识视频讲解

给定一个逆波兰表达式，求表达式的值。

数据范围：表达式长度满足 $1 \le n \le 10^4 \$ ，表达式中仅包含数字和 + ，- , * , / ，其中数字的大小满足 $|val| \le 200 \$ 。

示例1

输入

["2","1","+","4","*"]

输出

示例2

输入

["2","0","+"]

输出

算法知识视频讲解

Python 3

alex_coder

class Solution:
    def evalRPN(self , tokens: List[str]) -> int:
        # write code here
        stack = []
        for i in tokens:
            stack.append(i)
            if(stack[-1] in ['+','-','*','/']):
                operator = stack.pop()
                right = stack.pop()
                left = stack.pop()
                stack.append(str(int(eval(left+operator+right))))
        return int(stack[0])

发表于 2022-08-31 07:14:24 回复(0)

Python 3

初心者托奇

C++

class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        stack<int> stk;
        int tmp1, tmp2;
        for (auto i : tokens)
            if (i[0] < 48 && i.size() == 1)
            {
                tmp1 = stk.top();
                stk.pop();
                tmp2 = stk.top();
                stk.pop();
                if (i[0] == 42)
                    stk.push(tmp2 * tmp1);
                else if (i[0] == 43)
                    stk.push(tmp2 + tmp1);
                else if (i[0] == 45)
                    stk.push(tmp2 - tmp1);
                else
                    stk.push(tmp2 / tmp1);
            }
            else
                stk.push(stoi(i));
            return stk.top();
    }
};

Python

class Solution:
    def evalRPN(self , tokens: List[str]) -> int:
        stk = []
        for i in tokens:
            if ord(i[-1]) < 48:
                tmp = stk.pop()
                stk.append(str(int(eval((stk.pop() + i + tmp)))))
            else:
                stk.append(i)
        return int(stk[-1])

发表于 2022-08-10 21:36:09 回复(0)

Python 3

牛客64294041号

class Solution:
    def evalRPN(self , tokens: List[str]) -> int:
        # write code here
        if len(tokens) == 1:
            return int(tokens[0])
        l = []
        x = 0
        y = 0
        for i in tokens:
            if i not in '+-*/':
                l.append(i)
            else:
                x = l.pop()
                y = l.pop()
                # 一定要转为int
                res = int(eval(str(y) + str(i) + str(x)))
                l.append(res)
        return l[0]

发表于 2022-08-08 19:41:02 回复(0)

Python 3

学习37

class Solution:
def evalRPN(self , tokens: List[str]) -> int:
# write code here
if tokens:
token_list = ["+", "-", "*", "/"]
stack = []
for token in tokens:
if token in token_list:
if len(stack) >= 2:
first = stack.pop()
second = stack.pop()
result = eval(str(second) + str(token) + str(first))
stack.append(int(result))
elif len(stack) == 1:
return int(stack[-1])
else:
stack.append(token)
return int(stack[-1]) if stack else 0
else:
return 0

发表于 2022-08-03 14:54:29 回复(0)

Python 3

来牛客玩玩

class Solution:
    def evalRPN(self , tokens: List[str]) -> int:
        # write code here
        stack = []
        for token in tokens:
            if token == '+':
                stack.append(stack.pop()+stack.pop())
            elif token == '-':
                stack.append(-stack.pop()+stack.pop())
            elif token == '*':
                stack.append(stack.pop()*stack.pop())
            elif token == '/':
                stack.append(int(1/stack.pop()*stack.pop()))
            else:
                stack.append(int(token))
        return stack.pop()

发表于 2022-07-24 23:52:31 回复(0)

Python 3

江上_酒

num = []
caozuodict = {'+', '-', '*', '/'}
for item in tokens:
    if item in caozuodict:
        a = num.pop()
        b = num.pop()
        if item == '+':
            num.append(a+b)
        elif item == '-':
            num.append(b-a)
        elif item == '*':
            num.append(a*b)
        else:
            num.append(int(b/a))
    else:
        num.append(int(item))
print(num[0])

发表于 2022-07-14 16:07:56 回复(0)

Python 3

彬彬12345

#
# 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
def cal(a,b,op):
if op=="+":
return a+b
elif op=="-":
return a-b
elif op=='/':
return int(a/b)
elif op=="*":
return a*b
lst=[]
for i in tokens:
if i=="+" or i=="*" or i=="/" or i=="-":
b=lst.pop()
a=lst.pop()
lst.append(cal(a,b,i))
else:
lst.append(int(i))
return int(lst.pop())

发表于 2022-04-06 19:18:36 回复(0)

Python 3

长风～破浪

class Solution:
    def evalRPN(self , tokens: List[str]) -> int:
        # write code here
        ls = []
        for i in range(len(tokens)):
            if tokens[i] in ["+","-","*","/"]:
                l1 = ls.pop()
                l2 = ls.pop()
                res = str(int(eval(l2 + tokens[i] + l1)))
                ls.append(res)
            else:
                ls.append(tokens[i])
        return int(ls[-1])

发表于 2022-01-18 22:10:36 回复(1)