带括号的四则运算问题

  1 #include<iostream>
  2 #include<string>
  3 #include<vector>
  4 #include<algorithm>
  5 #include<stack>
  6 #include<map>
  7 #include<sstream>
  8 using namespace std;
  9 
 10 int calculator(string s)
 11 {
 12     s = "("+s+")";
 13     size_t len = s.size();
 14     stack<int> num;
 15     stack<char> oper;
 16     map<string, bool> priority;  //false时应该对放入栈顶的操作符进行运算，true时将新的操作符入栈
 17     priority["++"]=false;   
 18     priority["+-"]=false;
 19     priority["+*"]=true;
 20     priority["+/"]=true;
 21     priority["+("]=true;
 22     priority["+)"]=false;
 23 
 24     priority["-+"]=false;
 25     priority["--"]=false;
 26     priority["-*"]=true;
 27     priority["-/"]=true;
 28     priority["-("]=true;
 29     priority["-)"]=false;
 30 
 31     priority["*+"]=false;
 32     priority["*-"]=false;
 33     priority["**"]=false;
 34     priority["*/"]=false;
 35     priority["*("]=true;
 36     priority["*)"]=false;
 37 
 38     priority["/+"]=false;
 39     priority["/-"]=false;
 40     priority["/*"]=false;
 41     priority["//"]=false;
 42     priority["/("]=true;
 43     priority["/)"]=false;
 44 
 45     priority["(+"]=true;
 46     priority["(-"]=true;
 47     priority["(*"]=true;
 48     priority["(/"]=true;
 49     priority["(("]=true;
 50     priority["()"]=false;
 51   
 52     //int flag=1; //表示可以构造操作数
 53     string sp; //从s中提取操作数到sp中
 54     for(size_t i=0; i<len; i++)
 55     {
 56         if(s[i]=='+' || s[i]=='-' || s[i]=='*' || s[i]=='/' || s[i]=='(' || s[i]==')')
 57         {
 58             if(!sp.empty())
 59             {
 60                 int temp;
 61                 istringstream is(sp);
 62                 is>>temp;
 63                 num.push(temp);
 64                 sp.clear();
 65             }
 66 
 67             char c = s[i];
 68             if(oper.empty())
 69                 oper.push(c);
 70             else
 71             {
 72                 char ct = oper.top();
 73                 string str;
 74                 str.push_back(ct);
 75                 str.push_back(c);
 76                 if(true==priority[str])  //新的操作符入栈
 77                     oper.push(c);
 78                 else                     //对栈顶操作符进行计算
 79                 {
 80                     int a,b;
 81                     if(ct!='(')
 82                     {            
 83                         b = num.top();                    
 84                         num.pop();                    
 85                         a = num.top();
 86                         num.pop();
 87                     }
 88                     int res;
 89                     switch(ct)
 90                     {
 91                     case '+':
 92                         res = a+b;
 93                         num.push(res);
 94                         break;
 95                     case '-':
 96                         res = a-b;
 97                         num.push(res);
 98                         break;
 99                     case '*':
100                         res = a*b;
101                         num.push(res);
102                         break;
103                     case '/':
104                         res = a/b;
105                         num.push(res);
106                         break;
107                     case '(':
108                         if(c==')')
109                         {
110                             i++;
111                         }
112                     }
113                     oper.pop();
114                     i--;
115                 }
116             }
117         }
118         else
119             sp.push_back(s[i]);
120     }
121 
122     return num.top();
123 }
124 
125 int main()
126 {
127     string s="(5+21*(5-(15-10)*3)/5+5)";
128     int ans;
129     ans = calculator(s);
130     cout<<ans<<endl;
131     
132     return 0;
133 }
需要说明的是这里的a/b实现的是整数相除，比如说3/2得到的是1而不是1.5