Complicated Expression

  1 #include <iostream>
  2 //#include <string>
  3 #include <stack>
  4 #include <stdio.h>
  5 #include <string.h>
  6 
  7 using namespace std;
  8 
  9 typedef std::stack<std::string> strStack;
 10 typedef std::stack<double> valueStack;
 11 
 12 
 13 inline int parseStr(const char*& str, strStack &tempStack)
 14 {
 15     const char* begin = str;
 16     const char* p = str;
 17     while (*p)
 18     {
 19         char buf[50];
 20         if (*p == ‘(‘ || *p == ‘+‘ || *p == ‘-‘ || *p == ‘*‘)
 21         {
 22             buf[0] = *p;
 23             buf[1] = 0;
 24             tempStack.push(buf);
 25             if (p == begin)
 26                 ++begin;
 27         }
 28         else if (*p == ‘ ‘)
 29         {
 30             if (p == begin)
 31                 ++begin;
 32             else
 33             {
 34                 int size = p - begin;
 35                 strncpy(buf, begin, size);
 36                 buf[size] = 0;
 37                 tempStack.push(buf);
 38                 begin = p + 1;
 39             }
 40         }
 41         else if (*p == ‘)‘)
 42         {
 43             if (p != begin)
 44             {
 45                 int size = p - begin;
 46                 strncpy(buf, begin, size);
 47                 buf[size] = 0;
 48                 tempStack.push(buf);
 49                 begin = p + 1;
 50             }
 51             ++p;
 52             break;
 53         }
 54         else
 55         {
 56             // 可以做一些非法字符检查, 这题貌似不需要
 57         }
 58         ++p;
 59     }
 60     str = p;
 61     return 0;
 62 }
 63 
 64 
 65 inline int calAdd(strStack& stack, double&result)
 66 {
 67     if (stack.size() < 1)
 68         return -1;
 69 
 70     double r = 0;
 71     while (!stack.empty())
 72     {
 73         std::string str = stack.top();
 74         stack.pop();
 75         double val;
 76         sscanf(str.c_str(), "%lf", &val);
 77         r += val;
 78     }
 79     result = r;
 80     return 0;
 81 }
 82 
 83 inline int calSub(strStack& stack, double&result)
 84 {
 85     if (stack.size() < 1 || stack.size() > 2)
 86         return -1;
 87 
 88     std::string str = stack.top();
 89     stack.pop();
 90     double val1;
 91     sscanf(str.c_str(), "%lf", &val1);
 92     if (stack.size() == 0)
 93     {
 94         result = -val1;
 95         return 0;
 96     }
 97 
 98     str = stack.top();
 99     stack.pop();
100     double val2;
101     sscanf(str.c_str(), "%lf", &val2);
102     result = val1 - val2;
103 
104     return 0;
105 }
106 
107 inline int calMul(strStack& stack, double& result)
108 {
109     if (stack.size() < 1)
110         return -1;
111 
112     double r = 1;
113     while ( !stack.empty())
114     {
115         std::string str = stack.top();
116         stack.pop();
117         double val;
118         sscanf(str.c_str(), "%lf", &val);
119         r *= val;
120     }
121     result = r;
122     return 0;
123 }
124 
125 
126 // 成功返回0
127 int calSubOprator(strStack& stack, double &result)
128 {
129     int r = 0;
130     double val = 0;
131     std::string operaterStr = stack.top();
132     stack.pop();
133     if (operaterStr == "+")
134     {
135         r = calAdd(stack, val);
136     }
137     else if (operaterStr == "-")
138     {
139         r = calSub(stack, val);
140     }
141     else if (operaterStr == "*")
142     {
143         r = calMul(stack, val);
144     }
145     else
146         return -1;
147 
148     if (r == -1)
149         return -1;
150 
151     result = val;
152     return 0;
153 }
154 
155 inline int calcStr(strStack &tempStack, valueStack& resultStack)
156 {
157     strStack temp;
158     while (true)
159     {
160         if (tempStack.empty())
161             return -1;
162 
163         std::string str = tempStack.top();
164         if (str == "#")
165         {
166             double val = resultStack.top();
167             resultStack.pop();
168             tempStack.pop();
169             char buf[50];
170             sprintf(buf, "%d", int(val));
171             temp.push(buf);
172         }
173         else if (str == "(")
174         {
175             tempStack.pop();
176             break;
177         }
178         else
179         {
180             temp.push(tempStack.top());
181             tempStack.pop();
182         }
183     }
184 
185     double val;
186     if (calSubOprator(temp, val) == -1)
187         return -1;
188 
189     resultStack.push(val);
190     return 0;
191 }
192 
193 
194 int calc(const char* str, double &resultVal)
195 {
196     if (str == NULL || *str == 0)
197         return -1;
198 
199     const char* p = str;
200     strStack tempStr;
201     valueStack tempVal;
202 
203     while (true)
204     {
205         int r = 0;
206         r = parseStr(p, tempStr);
207         if (r == -1)
208             return -1;
209 
210         r = calcStr(tempStr, tempVal);
211         if (r == -1)
212             return -1;
213 
214         if (*p == 0)
215         {
216             if (tempStr.empty())
217             {
218                 resultVal = tempVal.top();
219                 tempVal.pop();
220             }
221             else
222                 return -1;
223             break;
224         }
225         else
226         {
227             // 临时结果入栈
228             tempStr.push("#");
229         }
230     }
231 
232     return 0;
233 }
234 
235 
236 int main()
237 {
238 
239     const char*arr[] = {
240         "(+ 1 (* 2 3)))",
241         "(2 3)",
242         "(- 3 2 1)",
243         "(+ (+ 1 2) (* 2 3) (- 2 1))",
244         "(- 2)"
245     };
246 
247 
248     for (int i = 0; i < 5; ++i)
249     {
250         const char* buf = arr[i];
251         double result = 0;
252         if (calc(buf, result) == 0)
253         {
254             cout << result << endl;
255         }
256         else
257         {
258             cout << "invalid expression" << endl;
259         }
260 
261     }
262 
263     return 0;
264 }