在C++中用STL实现简单计算器

最新推荐文章于 2023-12-09 10:52:20 发布

原创最新推荐文章于 2023-12-09 10:52:20 发布 · 269 阅读

0 ·

CC 4.0 BY-SA版权

本文介绍如何利用C++标准模板库(STL)构建一个基本的计算器，通过解析输入的数学表达式并进行运算。

在C++中用STL实现简单计算器

#include <iostream>

#include <stack>

using namespace std;

int Priority(char ch)

{

switch(ch)

{

case '(':

return 3;

case '*':

case '/':

return 2;

case '+':

case '-':

return 1;

default:

return 0;

}

int main()

{

int i = 0, tmp = 0, num1, num2, result;

stack<int> s_opt, s_num;

char opt[64] = {0};

char ch;

cout << "Please input :" << endl;

cin >> opt;

while (opt[i] != '\0' || s_opt.empty() != true)

{

if (opt[i] >= '0' && opt[i] <= '9')

{

tmp = tmp * 10 + opt[i] - '0';

i++;

if (opt[i] > '9' || opt[i] < '0')

{

s_num.push(tmp);

tmp = 0;

}

else

{

//操作符进栈

if (s_opt.empty() || (s_opt.top() == '(' && opt[i] != ')')

|| Priority(opt[i]) > Priority(s_opt.top()))

{

s_opt.push(opt[i]);

i++;

continue;

}

if (s_opt.top() == '(' && opt[i] == ')')

{

s_opt.pop();

i++;

continue;

}

if ((opt[i] == ')' && s_opt.top() != '(') ||

Priority(opt[i]) <= Priority(s_opt.top()) || (opt[i] == '\0' && !s_opt.empty()))

{

ch = s_opt.top();

s_opt.pop();

switch(ch)

{

case '+':

num1 = s_num.top();

s_num.pop();

num2 = s_num.top();

s_num.pop();

s_num.push(num1 + num2);

break;

case '-':

num1 = s_num.top();

s_num.pop();

num2 = s_num.top();

s_num.pop();

s_num.push(num2 - num1);

break;

case '*':

num1 = s_num.top();

s_num.pop();

num2 = s_num.top();

s_num.pop();

s_num.push(num1 * num2);

break;

case '/':

num1 = s_num.top();

s_num.pop();

num2 = s_num.top();

s_num.pop();

s_num.push(num2 / num1);

break;

}

result = s_num.top();

cout << result << endl;

return 0;

}