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 else33 {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 else43 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t254 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 else65 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 else80 t = t2 - t1;81 ds.push(t);82 }83 printf("%.2f\n", ds.top());84 }85 return 0;86 }
