简单题，直接模拟，但是还是要仔细点。。。
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1 #include <iostream> 2 #include <stack> 3 #include <iomanip> 4 #include <ios> 5 using namespace std; 6 7 int main() 8 { 9 double a; 10 while(cin >> a) 11 { 12 stack<double> Snum; 13 stack<char> Sop; 14 15 Snum.push(a); 16 char ch = getchar(); 17 if(a == 0 && ch == '\n') 18 break; 19 while(ch != '\n') 20 { 21 ch = getchar(); 22 Sop.push(ch); 23 cin >> a; 24 double tmp; 25 if(Sop.top() == '*') 26 { 27 tmp = a * Snum.top(); 28 Snum.pop(); 29 Snum.push(tmp); 30 Sop.pop(); 31 } 32 else if(Sop.top() == '/') 33 { 34 tmp = (Snum.top() / a); 35 Snum.pop(); 36 Snum.push(tmp); 37 Sop.pop(); 38 } 39 else 40 { 41 Snum.push(a); 42 } 43 ch = getchar(); 44 } 45 46 while(!Sop.empty()) 47 { 48 double n1 = Snum.top(); 49 Snum.pop(); 50 double n2 = Snum.top(); 51 Snum.pop(); 52 double tmp; 53 if(Sop.top() == '+') 54 { 55 Sop.pop(); 56 if(!Sop.empty() && Sop.top() == '-') 57 { 58 tmp = n2 - n1; 59 Snum.push(tmp); 60 } 61 else 62 { 63 tmp = n1 + n2; 64 Snum.push(tmp); 65 } 66 } 67 else if(Sop.top() == '-') 68 { 69 Sop.pop(); 70 if(!Sop.empty() && Sop.top() == '-') 71 { 72 tmp = n1 + n2; 73 Snum.push(tmp); 74 } 75 else 76 { 77 tmp = n2 - n1; 78 Snum.push(tmp); 79 } 80 } 81 } 82 83 double ans = Snum.top(); 84 streamsize pre = cout.precision(); 85 cout <<setprecision(2) << setiosflags(ios::fixed) << ans << setprecision(pre) << endl; 86 } 87 88 return 0; 89 }