1 #include <iostream>
2 #include<sstream>
3 using namespace std;
4 template<typename T>
5 class stack
6 {
7 T p[40];
8 int toop;
9 public:
10 stack() { toop = -1; }
11 void push(T t) { toop++; p[toop] = t; }
12 T top() { return p[toop]; }
13 bool empty() { if (toop == -1)return true; return false; }
14 void pop() { toop--; }
15 };
16 class caculator
17 {
18 string s;//原波兰式的容器
19 stack<char>op;
20 stack<float>num;
21 stringstream ss;//用于转换的流
22 stringstream sb;//插入逆波兰式的流
23 string str;//存放数字的容器，每次更新
24 string strs;//存放逆波兰式的容器
25 float x, y;
26 public:
27 caculator(char *p) { s = p; }
28 float trans(const char *p);
29 float antipoland();
30 void show() { cout << strs; }
31 void readnum();
32 void caucEveTime();
33 void shownum() { while (!num.empty()) { cout << num.top() << endl; num.pop(); } }
34 void showop() { while (!op.empty()) { cout << op.top() << endl; op.pop(); } }
35 };
36 float caculator::trans(const char *p)//底层const,对象为常量
37 {
38 float n;
39 n = *p - '\0' - 48;//确保转化成int后数值不变
40 int i = strlen(p);
41 while (--i)
42 {
43 *p++;
44 n = n * 10 + (*p - '\0' - 48);
45 }
46 return n;
47 }
48 void caculator::readnum()
49 {
50 str = ss.str();
51 if (!str.empty())//str中存放数字串
52 {
53 ss.str("");//清空流
54 num.push(trans(str.c_str()));
55 }
56 }
57 void caculator::caucEveTime()//由符号栈弹出符号决定调用
58 {
59 y = num.top();
60 num.pop();
61 x = num.top();
62 num.pop();
63 switch (op.top())
64 {
65 case'+':num.push(x + y); break;
66 case'-':num.push(x - y); break;
67 case'*':num.push(x*y); break;
68 case'/':num.push(x / y); break;
69 default:break;
70 }
71 }
72 float caculator::antipoland()
73 {
74 for (int i = 0; i < s.size(); i++)
75 switch (s[i])
76 {
77 case '(':op.push(s[i]);readnum(); break;
78 case '+':
79 case '-':
80 readnum();
81 if (op.top() == '(')
82 op.push(s[i]);
83 else if(op.empty())
84 op.push(s[i]);
85 else
86 {
87 while (!op.empty())
88 {
89 if (op.top() != '('&&op.top() != ')')
90 {
91 sb << op.top();
92 caucEveTime();
93 }
94 op.pop();
95 }
96 op.push(s[i]);
97 }
98 break;
99 case ')':
100 readnum();
101 while (op.top() != '(')
102 {
103 sb << op.top();
104 caucEveTime();
105 op.pop();
106 }op.pop(); break;
107 case '*':
108 case'/':
109 readnum();
110 while (op.top() == '*' || op.top() == '/')
111 {
112 sb << op.top();
113 caucEveTime();
114 op.pop();
115 }op.push(s[i]); break;
116 default:
117 sb << s[i];
118 ss <<s[i];
119 break;
120 }
121 str = ss.str();
122 num.push(trans(str.c_str()));
123 while (!op.empty())
124 {
125 if (op.top() != '('&&op.top() != ')')
126 {
127 sb<< op.top();
128 caucEveTime();
129 }
130 op.pop();
131 }
132
133 strs = sb.str();
134 return num.top();
135 }
136 void main()
137 {
138 char ch[40];
139 char *p=ch;
140 cin >> p;
141 caculator a(p);
142 //a.antipoland();//两次重复调用改变数字栈中的数字！
143 // a.show();
144 cout <<"="<<a.antipoland()<<endl;
145 // cout << endl;
146 //a.shownum();
147 //a.showop();
148 }
