ONP, C++ (gcc) - rextester

ONP

//g++  4.9.3

#include <iostream>
#include <sstream>
#include <vector>

struct Operation_ID
{
    constexpr static int
        Add=0,
        Sub=1,
        Multiple=2,
        Divide=3;
};

struct Option
{
    int Type=0;
    Option(){;}
};

struct IntVar : Option
{
    int Value;
    IntVar(int NewValue)
    {
        Type=1;
        Value=NewValue;
    }
};

struct Operation : Option
{
    int ID;
    Operation(int newID)
    {
        Type=2;
        ID=newID;
    }
};

struct CalcMachine
{
    std::vector<Option*> Sketch;
    std::vector<float> Stack;
    std::vector<int> Oprs;
    
    CalcMachine()
    {
        /*
        Sketch.push_back(new IntVar(2));
        Sketch.push_back(new IntVar(2));
        Sketch.push_back(new IntVar(2));
        Sketch.push_back(new Operation(Operation_ID::Multiple));
        Sketch.push_back(new Operation(Operation_ID::Add));
        */
    }
    
    void AddOperation(int ID)
    {
        if(ID!=-1)
        {
            if(!Oprs.size()||Oprs.back()/2<ID/2)
            {
                Oprs.push_back(ID);
            }
            else
            {
                while(Oprs.size() && Oprs.back()>ID)
                {
                    Sketch.push_back(new Operation(Oprs.back()));
                    Oprs.pop_back();
                }
            }
        }
        
        //Sketch.push_back(new Operation(ID));
    }
    
    void AddIntVar(int Value)
    {
        Sketch.push_back(new IntVar(Value));
    }
    
    float Run()
    {
        AddOperation(-1);
        for(size_t i=0; i<Sketch.size(); ++i)
        {
            Option *Obj=Sketch[i];
            switch(Obj->Type)
            {
                case 1:
                    Stack.push_back(static_cast<IntVar*>(Obj)->Value);
                break;
                case 2:
                    int ID=static_cast<Operation*>(Obj)->ID;
                    if(ID==Operation_ID::Add)
                    {
                        float Value=Stack.back();
                        Stack.pop_back();
                        Stack.back()+=Value;
                    }
                    else if(ID==Operation_ID::Sub)
                    {
                        float Value=Stack.back();
                        Stack.pop_back();
                        Stack.back()-=Value;
                    }
                    else if(ID==Operation_ID::Multiple)
                    {
                        float Value=Stack.back();
                        Stack.pop_back();
                        Stack.back()*=Value;
                    }
                    else if(ID==Operation_ID::Divide)
                    {
                        float Value=Stack.back();
                        Stack.pop_back();
                        Stack.back()/=Value;
                    }
                break;
            }
        }
        if(Stack.size()) 
        {
            float Ret=Stack.back();
            Stack.pop_back();
            return Ret;
        }
        else return 0;
    }
};

// 2 + 2 * 2

// 2 2 2 * +

// 1 [0] 1 [1] 1 [2] 2 [*] 2 [+]

int main()
{
    CalcMachine CM;
    CM.AddIntVar(2);
    CM.AddIntVar(Operation_ID::Add);
    CM.AddIntVar(2);
    CM.AddIntVar(Operation_ID::Multiple);
    CM.AddIntVar(2);
    std::cout<<CM.Run()<<'\n';
}


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