Imitation LISP operations | c ++

 

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 /**
 4  *  仿LISP运算
 5  *  模拟(sub (mul 2 4) (div 9 3))
 6  * @return
 7  */
 8 
 9 int main() {
10     int mark = 0;
11     int num1,num2;
12     string str;
13     stack<int> numStatck;
14     stack<string> operStack;
15 
16     getline(cin,str);
17     for(int i = 0; i < str.length() ; i++)
18     {
19         char c = str[i];
20         cout<<c<<" ";
21         if(c == '(') {
22             operStack.push(str.substr(i+1,3));
23             i += 4;
24             mark =  i + 1;
25         } else if(c == ')') {
26             if(mark < i) {
27                 //stoi string --> int
28                 numStatck.push(stoi(str.substr(mark,i-mark)));
29 
30                 i++;
31                 mark = i + 1;
32             }
33             num1 = numStatck.top();
34             numStatck.pop();
35             num2 = numStatck.top();
36             numStatck.pop();
37             string ex = operStack.top();
38             operStack.pop ();
39  
40              if (ex == " add " )
 41                  numStatck.push (num1 + num2);
42              else  if (f == " sub " )
 43                  numStatck.push (num1- num2);
44              else  if (f == " mul " )
 45                  numStatck.push (* num1 num2);
46              else  if (f ==   " div " )
 47                  if (num2 ==0) cout <<"ERROR"<<endl;
48                 else
49                     numStatck.push(num2/num1);
50 
51         } else {
52             if(c == ' ') {
53                 if(mark < i ) {
54                     numStatck.push(stoi(str.substr(mark,i-mark)));
55                     mark = i + 1;
56                 }
57             }
58         }
59     }
60     cout<<"结果：";
61     cout<<numStatck.top()<<endl;
62     return 0;
63 }