学步园

表达式求值~

#include <cstdio>
  2 #include <cstring>
  3 #include <stack>
  4 usingnamespace std;
  5 
  6 struct num
  7 {
  8 int u,d;
  9 };
 10 
 11 stack<struct num> NUM;
 12 stack<char> OPP;
 13 
 14 constint LEN =1024;
 15 
 16 char input[LEN];
 17 
 18 void MyClear()
 19 {
 20 while (!NUM.empty()) NUM.pop();
 21 while (!OPP.empty()) OPP.pop();
 22 }
 23 
 24 int gcd(int a,int b)
 25 {
 26 if (a ==0) return b;
 27 elsereturn gcd(b % a,a);
 28 }
 29 
 30 struct num work(struct num & a,struct num & b,char opp)
 31 {
 32 struct num ans;
 33 if (opp =='&')
 34     {
 35         ans.u = a.u * b.d + a.d * b.u;
 36         ans.d = a.d * b.d;
 37 int tmp = gcd(ans.u,ans.d);
 38         ans.u /= tmp;
 39         ans.d /= tmp;
 40     }
 41 else
 42     {
 43 struct num ians;
 44         ians.u = a.u * b.d + a.d * b.u;
 45         ians.d = a.u * b.u;
 46 int tmp = gcd(ians.u,ians.d);
 47         ans.u = ians.d / tmp;
 48         ans.d = ians.u / tmp;
 49     }
 50 return ans;
 51 }
 52 int main()
 53 {
 54 struct num in;
 55 while (gets(input))
 56     {
 57         MyClear();
 58 int length = strlen(input);
 59 for (int i = length -1;i >=0;i--)
 60         {
 61 if (input[i] =='') continue;
 62 if (input[i] ==')'|| input[i] =='&'|| input[i] =='|')
 63                 OPP.push(input[i]);
 64 elseif (input[i] >='0'&& input[i] <='9')
 65             {
 66 while (input[i] !='/') i--;
 67                 i--;
 68 while (input[i] >='0'&& input[i] <='9'&& i >=0) i--;
 69                 i++;
 70                 sscanf(input + i,"%d/%d",&in.u,&in.d);
 71                 NUM.push(in);
 72             }
 73 elseif (input[i] =='(')
 74             {
 75 while (OPP.top() !=')')
 76                 {
 77 char opp = OPP.top();
 78                     OPP.pop();
 79 struct num num1 = NUM.top();
 80                     NUM.pop();
 81 struct num num2 = NUM.top();
 82                     NUM.pop();
 83 struct num ans = work(num1,num2,opp);
 84                     NUM.push(ans);
 85                 }
 86                 OPP.pop();
 87             }
 88         }
 89 while (!OPP.empty())
 90         {
 91 char opp = OPP.top();
 92             OPP.pop();
 93 struct num num1 = NUM.top();
 94             NUM.pop();
 95 struct num num2 = NUM.top();
 96             NUM.pop();
 97 struct num ans = work(num1,num2,opp);
 98             NUM.push(ans);
 99         }
100 in= NUM.top();
101 int tmp = gcd(in.u,in.d);
102         printf("%d/%d\n",in.u / tmp,in.d / tmp);
103     }
104 return0;
105 }