Calculator

  1 //============================================================================
  2 // Name        : calculator.cpp
  3 // Author      : 
  4 // Version     :
  5 // Copyright   : Your copyright notice
  6 // Description : Hello World in C++, Ansi-style
  7 //============================================================================
  8 
  9 #include <string>
 10 #include <sstream>
 11 #include <stack>
 12 #include <vector>
 13 #include <iostream>
 14 #include <iterator>
 15 #include <stdexcept>
 16 #include <algorithm>
 17 
 18 using namespace std;
 19 
 20 bool CheckBlank(const char c)
 21 {
 22     return c == ‘ ‘;
 23 }
 24 
 25 bool CheckInvalid(const char c)
 26 {
 27     if(c >= ‘0‘ && c <= ‘9‘)
 28         return false;
 29     else if(c == ‘+‘ || c == ‘-‘ || c == ‘*‘ || c == ‘/‘ ||
 30             c == ‘(‘ || c == ‘)‘)
 31         return false;
 32     else
 33         return true;
 34 }
 35 
 36 bool CheckOperator(const char c)
 37 {
 38     if(c == ‘+‘ || c == ‘-‘ || c == ‘*‘ || c == ‘/‘)
 39         return true;
 40     else
 41         return false;
 42 }
 43 
 44 bool CheckNotNumber(const char c)
 45 {
 46     if(c < ‘0‘ || c > ‘9‘)
 47         return true;
 48     else
 49         return false;
 50 }
 51 
 52 int main() {
 53     string str_in, str;
 54     getline(cin, str_in);
 55     remove_copy_if(str_in.begin(), str_in.end(), back_inserter(str), CheckBlank);
 56     try{
 57         if(str.end() != find_if(str.begin(), str.end(), CheckInvalid))
 58             throw runtime_error("Expression Invalid(0)!");
 59         if(0 == str.size() || CheckOperator(str[0]) || str[0] == ‘)‘)
 60             throw runtime_error("Expression Invalid(1)!");
 61         if(count(str.begin(), str.end(), ‘(‘) != count(str.begin(), str.end(), ‘)‘))
 62             throw runtime_error("Expression Invalid(2)!");
 63     }catch(runtime_error &err){
 64         cout<<err.what();
 65         exit(0);
 66     }
 67 
 68     vector<string> vect;
 69     stack<char> ops;
 70     string::iterator i = str.begin(), j;
 71     while(i != str.end())
 72     {
 73         j = find_if(i, str.end(), CheckNotNumber);
 74         if(i == j)
 75         {
 76             if(ops.empty() || ‘(‘ == *i)
 77                 ops.push(*i);
 78             else if(‘)‘ == *i)
 79             {
 80                 while(0 != ops.size())
 81                 {
 82                     if(ops.top() != ‘(‘)
 83                     {
 84                         string in(" ");
 85                         in[0] = ops.top();
 86                         vect.push_back(in);
 87                     }
 88                     ops.pop();
 89                 }
 90             }
 91             else if(‘+‘ == *i || ‘-‘ == *i)
 92             {
 93                 if(‘(‘ == ops.top())
 94                     ops.push(*i);
 95                 else if(CheckNotNumber(ops.top()))
 96                 {
 97                     string in(" ");
 98                     in[0] = ops.top();
 99                     vect.push_back(in);
100                     ops.pop();
101                     ops.push(*i);
102                 }
103             }
104             else if(‘*‘ == *i || ‘/‘ == *i)
105             {
106                 if(‘*‘ == ops.top() || ‘/‘ == ops.top())
107                 {
108                     string in(" ");
109                     in[0] = ops.top();
110                     vect.push_back(in);
111                     ops.pop();
112                 }
113                 ops.push(*i);
114             }
115             j++;
116         }
117         else
118         {
119             string in(i, j);
120             vect.push_back(in);
121         }
122         i = j;
123     }
124     while(ops.size())
125     {
126         string in(" ");
127         in[0] = ops.top();
128         vect.push_back(in);
129         ops.pop();
130     }
131 
132     stack<int> stk;
133     for(vector<string>::size_type i = 0; i < vect.size(); i++)
134     {
135         if(CheckNotNumber(vect[i][0]))
136         {
137             int l, r, result;
138             r = stk.top();
139             stk.pop();
140             l = stk.top();
141             stk.pop();
142             switch(vect[i][0])
143             {
144             case ‘+‘:
145                 result = l + r;
146                 break;
147             case ‘-‘:
148                 result = l - r;
149                 break;
150             case ‘*‘:
151                 result = l * r;
152                 break;
153             case ‘/‘:
154                 result = l / r;
155                 break;
156             }
157             stk.push(result);
158         }
159         else
160         {
161             int value;
162             stringstream ss(vect[i]);
163             ss >> value;
164             stk.push(value);
165         }
166     }
167 
168     cout<<"result:"<<stk.top()<<endl;
169     return 0;
170 }