九度 27 简单计算器栈

最新推荐文章于 2019-03-05 15:39:30 发布

转载最新推荐文章于 2019-03-05 15:39:30 发布 · 307 阅读

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不知道为啥这个会报错deque iterator not dereferencable

#include <iostream>
#include <algorithm>
#include<string>
#include<stack>

using namespace std;
char str[210];
int prio[5][5] = {
   1, 0, 0, 0, 0,//0自定义
   1, 0, 0, 0, 0,//1 "+"
   1, 0, 0, 0, 0,//2 "-"
   1, 1, 1, 0, 0,//3 “*”
   1, 1, 1, 0, 0
};
stack<int>op; //村运算符编号
stack<double>num;//表达式数字
double cal(int t){
   double a = num.top();
   num.pop();
   double b = num.top();
   num.pop();
   double ret;
   switch (t)
   {
   case 1:ret = a + b; break;
   case 2:ret = b - a; break;
   case 3:ret = a * b; break;
   case 4:ret = b / a; break;
   }
   return ret;
}
void main()
{
   while (gets(str)){
       if (str[0] = '0' && str[1] == 0)
           return;
       int i = 0;
       int len = strlen(str);
       int n = 0;//数字
       int t = 0;
       while (i < len){
           n = 0;
           while (str[i] == ' ')
               i++;

           while (str[i] >= '0'&&str[i]<='9'&&i < len)
           {
               n += n* 10 + str[i] - '0';
               i++;
           }
           num.push(n);
           while (str[i] == ' ')
               i++;
           if (str[i] == '+')
               t = 1;
           else if (str[i] == '-')
               t = 2;
           else if (str[i] == '*')
               t = 3;
           else if (str[i] == '/')
               t = 4;
           //优先级高于栈顶
           if (prio[t][op.top()] == 1 || op.empty())
               op.push(t);
           else{
               while (prio[t][op.top()] == 0)
               {
                   int tmp = op.top();
                   op.pop();
                   num.push(cal(tmp));
               }
               op.push(t);
           }
           i++;
       }
       while (!op.empty())
       {
           int tmp = op.top();
           op.pop();
           num.push(cal(tmp));
       }

       cout.precision(2);
       cout << fixed << num.top() << endl;
       num.pop();

   }


}

正确代码：

#include <iostream>
#include <algorithm>
#include<string>
#include<stack>
using namespace std;

char str[210];
stack<char>op; //运算fu
stack<double>num;//表达式数字
double cal(char t){
   double a = num.top();
   num.pop();
   double b = num.top();
   num.pop();
   double ret;
   switch (t)
   {
   case '+':ret = a + b; break;
   case '-':ret = b - a; break;
   case '*':ret = a * b; break;
   case '/':ret = b/ a; break;
   }
   return ret;
}

void main()
{
   int len,i;
   char oper;
   while (gets(str)){

       len = strlen(str);
       if (str[0] == '0' && str[1]==0)
           return;
       i = 0;

       int n = 0;//数字
       int t = 0;

       while (i < len){
           n = 0;
           while (str[i] == ' ')
               i++;

           while (str[i] >= '0'&&str[i]<='9'&&i < len)
           {
               n = n* 10 + str[i] - '0';
               i++;
           }
           num.push(n);
           while (str[i] == ' ')
               i++;
           switch (str[i]){//处理操作符
           case '+': case '-'://如果操作符为优先级最低的加减
               while (!op.empty()){//比此操作符优先级高或者相等，此题中所有操作符都符合此条件，略去
                   oper = op.top();//弹出栈顶操作符
                   op.pop();
                   num.push(cal(oper));//将结果压入堆栈
               }
               op.push(str[i]);
               break;
           case '*': case '/'://如果操作符为优先级第一的乘除
               //while (!op.empty() && (op.top() == '*' || op.top() == '/')){//比此操作符优先级高或者相等
               //   oper = op.top();//弹出栈顶操作符
               //   op.pop();
               //   num.push(cal(oper));//将结果压入堆栈
               //}
               op.push(str[i]);
               break;
           default:
               break;
           }

           i++;
       }
       while (!op.empty())
       {
           int tmp = op.top();
           op.pop();
           num.push(cal(tmp));
       }
       printf("%.2lf\n", num.top());
       /*cout.precision(2);
       cout << fixed << num.top() << endl;*/
       num.pop();