YB5.10 Решение задачи для частного примера

RobertDeMilo

Apr 14th, 2024

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#include <iostream>
#include <string>
#include <memory>
using namespace std;
class Node
{
public:
virtual int Evaluate()
{
return 0;
}
};
class Digit: public Node
{
public:
Digit(int d):d_(d){}
int Evaluate() override
{
return d_;
}
private:
const int d_;
};
class Variable: public Node
{
public:
Variable(const int&x):x_(x){}
int Evaluate() override
{
return x_;
}
private:
const int &x_; // сохраняем ссылку на некторую внешнюю переменную
};
class Operation: public Node
{
public:
//Operation(Node&, Node&)
Operation(char op,shared_ptr<Node> left, shared_ptr<Node> right):
op_(op), left_(left), right_(right)
{
}
int Evaluate() override
{
if(op_=='*')
{
return left_->Evaluate() * right_->Evaluate();
}
else if(op_=='+')
{
return left_->Evaluate() + right_->Evaluate();
}
else if(op_=='-')
{
return left_->Evaluate() - right_->Evaluate();
}
return 0;
}
private:
const char op_;
shared_ptr<Node> left_, right_;
};
Node Parse(const string& tokens, int& x)
{
}
int main()
{
string tokens = "5+7-x*x+x";
//cout<<"Enter experssion: ";
//cin>>tokens;
int x;
//auto expr = Parse(tokens, x);
shared_ptr<Node> var1 = make_shared<Variable>(x);
shared_ptr<Node> var2 = make_shared<Variable>(x);
shared_ptr<Node> mul1 = make_shared<Operation>('*',var1, var2);
shared_ptr<Node> dig1 = make_shared<Digit>(5);
shared_ptr<Node> dig2 = make_shared<Digit>(7);
shared_ptr<Node> var3 = make_shared<Variable>(x);
shared_ptr<Node> plus1 = make_shared<Operation>('+',dig1, dig2);
shared_ptr<Node> minus1 = make_shared<Operation>('-', plus1, mul1);
shared_ptr<Node> plus2 = make_shared<Operation>('+', minus1, var3);
cout<<"Enter x: ";
while (cin>>x)
{
cout<<plus2->Evaluate()<<endl;
}
}

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