1 #include <iostream> 2 #include <cstdio> 3 #include <string> 4 #include <stack> 5 using namespace std; 6 int main() 7 { 8 string s; 9 while (getline(cin, s) && s != "0") 10 { 11 stack<double> ds; 12 stack<char> cs; 13 double t, t1, t2; 14 char c; 15 string::size_type i; 16 for (i = 0; i < s.size(); ++i) 17 { 18 if (s[i] >= '0' && s[i] <= '9') 19 { 20 t = 0; 21 while (s[i] >= '0' && s[i] <= '9') 22 { 23 t = t * 10 + s[i] - '0'; 24 ++i; 25 } 26 ds.push(t); 27 } 28 else if (s[i] == '+' || s[i] == '-') 29 { 30 if (cs.empty()) 31 cs.push(s[i]); 32 else 33 { 34 t1 = ds.top(); 35 ds.pop(); 36 t2 = ds.top(); 37 ds.pop(); 38 c = cs.top(); 39 cs.pop(); 40 if (c == '+') 41 t = t1 + t2; 42 else 43 t = t2 - t1; 44 ds.push(t); 45 cs.push(s[i]); 46 } 47 } 48 else if (s[i] == '*' || s[i] == '/') 49 { 50 bool ismul = 0; //标记是乘号还是除号 51 if (s[i] == '*') 52 ismul = 1; 53 i += 2; //求下个数字t2 54 t2 = 0; 55 while (s[i] >= '0' && s[i] <= '9') 56 { 57 t2 = t2 * 10 + s[i] - '0'; 58 ++i; 59 } 60 t1 = ds.top(); 61 ds.pop(); 62 if (ismul) 63 t = t1 * t2; 64 else 65 t = t1 / t2; 66 ds.push(t); 67 } 68 } 69 while (!cs.empty()) //处理剩下的加减号 70 { 71 t1 = ds.top(); 72 ds.pop(); 73 t2 = ds.top(); 74 ds.pop(); 75 c = cs.top(); 76 cs.pop(); 77 if (c == '+') 78 t = t1 + t2; 79 else 80 t = t2 - t1; 81 ds.push(t); 82 } 83 printf("%.2f\n", ds.top()); 84 } 85 return 0; 86 }
