华为机试 - 火星计算器

火星计算器：
   火星人使用运算符：@ # $ &
   优先级为：@ > # > $ > &
   
   X@Y = (X+1)*(Y+2)
   X#Y = (2X+3)*(3Y+4)
   X$Y = (3X+11)*(2Y+7)
   X&Y = (5X+20)*(4Y+1)
   
   X#Y@Z = X#(Y@Z)
   
   编写火星计算器程序，计算火星文表达式；
   
   例子：
   输入：1@2

   输出：8 

#include <iostream>#include <string>#include <stack>using namespace std;int changeOp(char op){switch (op){case '&':return 1;case '$':return 2;case '#':return 3;case '@':return 4;}return 0;}int cal(int num1, int num2, int op){switch(op){case 1:return (5*num1+20)*(4*num2+1);case 2:return (3*num1+11)*(2*num2+7);case 3:return (2*num1+3)*(3*num2+4);case 4:return (num1+1)*(num2+2);}return 0;}int main(){string str;cin>>str;stack<int> numStack;stack<int> opStack;int num=0;char op;for (unsigned i=0;i<str.size();i++){if (str[i]>='0'&&str[i]<='9')num=num*10+str[i]-'0';else{op=str[i];numStack.push(num);num=0;if (numStack.size()==1){opStack.push(changeOp(op));continue;}int curOp=changeOp(op);int prevOp=opStack.top();if(prevOp>=curOp){int num1=numStack.top();numStack.pop();int num2=numStack.top();numStack.pop();numStack.push(cal(num1,num2,prevOp));opStack.pop();opStack.push(curOp);}else{opStack.push(curOp);}}}numStack.push(num);while (!opStack.empty()){int num1=numStack.top();numStack.pop();int num2=numStack.top();numStack.pop();numStack.push(cal(num2,num1,opStack.top()));opStack.pop();}cout<<numStack.top()<<endl;system("pause");return 0;}