Всем привет, хотел бы попросить помощи у вас. Ниже код реализации бинарного дерева выражения. Задач заключается в том, что нужно написать функцию, которая по выражению а+b*(b-d) сделать (-а)+b*(b-d).
Например: я ввожу в префиксальное форме выражение 3+4*(7-4), то есть +*-7473, где а = 3, b= 4, d = 7 И надо сделать чтобы а = (- а), то есть ( -3) + 4 * (7-4).
Буду очень благодарен вам за помощь!!!
| C++ (Qt) |
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| #include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
using namespace std;
/** class TreeNode **/
class TreeNode
{
public:
char data;
TreeNode *left, *right;
/** constructor **/
TreeNode(char data)
{
this->data = data;
this->left = NULL;
this->right = NULL;
}
};
/** class StackNode **/
class StackNode
{
public:
TreeNode *treeNode;
StackNode *next;
/** constructor **/
StackNode(TreeNode *treeNode)
{
this->treeNode = treeNode;
next = NULL;
}
};
class ExpressionTree
{
private:
StackNode *top;
public:
/** constructor **/
ExpressionTree()
{
top = NULL;
}
/** function to clear tree **/
void clear()
{
top = NULL;
}
/** function to push a node **/
void push(TreeNode *ptr)
{
if (top == NULL)
top = new StackNode(ptr);
else
{
StackNode *nptr = new StackNode(ptr);
nptr->next = top;
top = nptr;
}
}
/** function to pop a node **/
TreeNode *pop()
{
if (top == NULL)
{
cout<<"Underflow"<<endl;
}
else
{
TreeNode *ptr = top->treeNode;
top = top->next;
return ptr;
}
}
/** function to get top node **/
TreeNode *peek()
{
return top->treeNode;
}
/** function to insert character **/
void insert(char val)
{
if (isDigit(val))
{
TreeNode *nptr = new TreeNode(val);
push(nptr);
}
else if (isOperator(val))
{
TreeNode *nptr = new TreeNode(val);
nptr->left = pop();
nptr->right = pop();
push(nptr);
}
else
{
cout<<"Invalid Expression"<<endl;
return;
}
}
/** function to check if digit **/
bool isDigit(char ch)
{
return ch >= '0' && ch <= '9';
}
/** function to check if operator **/
bool isOperator(char ch)
{
return ch == '+' || ch == '-' || ch == '*' || ch == '/';
}
/** function to convert character to digit **/
int toDigit(char ch)
{
return ch - '0';
}
/** function to build tree from input */
void buildTree(string eqn)
{
for (int i = eqn.length() - 1; i >= 0; i--)
insert(eqn[i]);
}
/** function to evaluate tree */
double evaluate()
{
return evaluate(peek());
}
/** function to evaluate tree */
double evaluate(TreeNode *ptr)
{
if (ptr->left == NULL && ptr->right == NULL)
return toDigit(ptr->data);
else
{
double result = 0.0;
double left = evaluate(ptr->left);
double right = evaluate(ptr->right);
char op = ptr->data;
switch (op)
{
case '+':
result = left + right;
break;
case '-':
result = left - right;
break;
case '*':
result = left * right;
break;
case '/':
result = left / right;
break;
default:
result = left + right;
break;
}
return result;
}
}
/** function to get postfix expression */
void postfix()
{
postOrder(peek());
}
/** post order traversal */
void postOrder(TreeNode *ptr)
{
if (ptr != NULL)
{
postOrder(ptr->left);
postOrder(ptr->right);
cout<<ptr->data;
}
}
/** function to get infix expression */
void infix()
{
inOrder(peek());
}
/** in order traversal */
void inOrder(TreeNode *ptr)
{
if (ptr != NULL)
{
inOrder(ptr->left);
cout<<ptr->data;
inOrder(ptr->right);
}
}
/** function to get prefix expression */
void prefix()
{
preOrder(peek());
}
/** pre order traversal */
void preOrder(TreeNode *ptr)
{
if (ptr != NULL)
{
cout<<ptr->data;
preOrder(ptr->left);
preOrder(ptr->right);
}
}
};
/** Main Contains menu **/
int main()
{
string s;
cout<<"Expression Tree Test"<<endl;
ExpressionTree et;
cout<<"\nEnter equation in Prefix form: ";
cin>>s;
et.buildTree(s);
cout<<"\nPrefix : ";
et.prefix();
cout<<"\n\nInfix : ";
et.infix();
cout<<"\n\nPostfix : ";
et.postfix();
cout<<"\n\nEvaluated Result : "<<et.evaluate();
return 0;
} |
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