Calculator（後綴表達式）

原創

薄帷清风

2020-02-20 13:12

【題目要求】

Implement a calculator program based on a Reverse Polish notation.

【輸入】

There could be several lines. Each line contains a Reverse Polish notation. The operators and operands are sepertated by spaces( there could be more than 1 spaces between input tokens).

1 2 3 - + *
1 -
2 0 /
-
1 2 +
2.2 3.25 1.1 2.5 / - 1.32 * +

【輸出】

Output result of each test case and keep 4 numbers after the decimal point.
Output ‘ERROR’ if there are errors of the input test case.

ERROR
ERROR
ERROR
ERROR
3.0000
5.9092

【我的程序】

#include <stdio.h>
#include <iostream>
#include <iomanip>
#define maxSize 500
using namespace std;

class myCal
{
    private:
        int depth;
        double a[maxSize];

    public:
        myCal() { depth=-1; }

        void init() { depth=-1; }
        int getDepth() { return depth; }
        double getData() { return a[depth]; }

        void myPush(double t) { a[++depth]=t; }
        int myPlus() { if (depth<1) return 1; a[depth-1]+=a[depth]; depth--; return 0; }
        int myMinus() { if (depth<1) return 1; a[depth-1]-=a[depth]; depth--; return 0; }
        int myMultiple() { if (depth<1) return 1; a[depth-1]*=a[depth]; depth--; return 0; }
        int myDivide() { if (depth<1) return 1; if (a[depth]==0) return 1; a[depth-1]/=a[depth]; depth--; return 0; }
};

int main()
{
    char ch;
    double t;
    int flag=0;
    myCal my;

    cout << fixed << setprecision(4);
    do
    {
        ch=cin.get();

        if (ch=='\n')
        {
            if (flag==0 && my.getDepth()==0) cout<< my.getData() << endl;
            else cout<< "ERROR" << endl;
            flag=0;
            my.init();
        }

        if ((ch<='9' && ch>='0') || ch=='.') { cin.putback(ch); cin>>t; my.myPush(t); }

        if (ch=='+' && flag==0) flag=my.myPlus();
        if (ch=='-' && flag==0) flag=my.myMinus();
        if (ch=='*' && flag==0) flag=my.myMultiple();
        if (ch=='/' && flag==0) flag=my.myDivide();

    }while (ch!=EOF);
    return 0;
}