1 #include<iostream>
2 #include<string>
3 using namespace std;
4
5 template<typename T>
6 class Stack
7 {
8 private:
9 T stack[100];
10 int i = 0;
11 public:
12 Stack() = default;
13
14 T pop()
15 {
16 if (i == -1)
17 {
18 cout << "栈已空！" << endl;
19 return 0;
20 }
21
22 T top = stack[i - 1];
23 --i;
24 return top;
25 }
26
27 void push(T num)
28 {
29 ++i;
30 stack[i - 1] = num;
31 }
32
33 void clear()
34 {
35 for (int j = 0; j < 100; ++j)
36 {
37 T[j] = 0;
38 }
39 }
40 };
41
42 int main()
43 {
44 Stack<string> ops;
45 Stack<double> num;
46 string str;
47
48 std::cout << "请输入计算式： " << endl;
49 cout << "注： 每个字符间请以空格分开，子表达式请用括号括起注明" << endl;
50 cout << "字符 E 代表结束" << endl;
51 while (true)
52 {
53 cin >> str;
54 if (str == "(") continue;
55 else if (str == "+") ops.push(str);
56 else if (str == "-") ops.push(str);
57 else if (str == "*") ops.push(str);
58 else if (str == "/") ops.push(str);
59 else if (str == ")")
60 {
61 string op = ops.pop();
62 double val = num.pop();
63 if (op == "+") val = num.pop() + val;
64 if (op == "-") val = num.pop() - val;
65 if (op == "*") val = num.pop() * val;
66 if (op == "/") val = num.pop() / val;
67 num.push(val);
68 }
69
70 else if (str != "E")
71 {
72 double val = stod(str);
73 num.push(val);
74 }
75
76 if (str == "E")
77 {
78 break;
79 }
80 }
81
82 cout << "结果为： ";
83 cout << num.pop() << endl;
84
85 return 0;
86 }
