تبديل infix به postfix

[Yas]

با سلام سورس برنامه تبديل عبارت infix‌به postfix را ميخواستم البته خودم با سوييچ نوشتم مي خواستم بدونم با دستور if چطوري ميشه نوشت؟

[كیانی]

سلام
کدی که نوشتید رو درج کنید.

یا علی(ع)

[Yas]

کد:

#include<iostream.h>
#include<conio.h>
#include<stack.hpp>
void evaluate(char a[])
{
stack st;
char ch;
for(int i=0;a[i]!='\0' ;i++)
{
switch(a[i])
{
case '+':
ch=st.display();
if(st.empty()==true || ch=='(')
st.push('+');
else
{
cout<<st.pop();
i--;
}
break;
case '-':
ch=st.display();
if(st.empty()==true || ch=='(')
st.push('-');
else
{
cout<<st.pop();
i--;
}
break;
case '*':
ch=st.display();
if(ch=='*' || ch=='/')
{
cout<<st.pop();
i--;
}
else
st.push('*');
break;
  case '/':
ch=st.display();
if(ch=='*' || ch=='/')
{
cout<<st.pop();
i--;
}
else
st.push('/');
break;
  case '(':
st.push('(');
break;
  case ')':
ch=st.pop();
while(ch!='(')
{
cout<<ch;
ch=st.pop();
}
break;
 default:
cout<<a[i];
break;
}
}
while(st.empty()==false)
cout<<st.pop();
}
int main()
{
  char infix[50];
  cout<<"\n"," enter infix string : ";
  cin>>infix;
  evaluate(infix);
  return 0 ;
}

[آرین]

با سلام

کد:

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

void Convert(const string & Infix, string & Postfix);
bool IsOperand(char ch);
bool TakesPrecedence(char OperatorA, char OperatorB);

int main(void)
{
char Reply;
do
{
string Infix, Postfix; // local to this loop
cout << "Enter an infix expression (e.g. (a+b)/c^2, with no
spaces):"
<< endl;
cin >> Infix;
Convert(Infix, Postfix);
cout << "The equivalent postfix expression is:" << endl
<< Postfix << endl;
cout << endl << "Do another (y/n)? ";
cin >> Reply;
}
while (tolower(Reply) == 'y');
return 0;
}

/*
Given: ch A character.
Task: To determine whether ch represents an operand (here
understood to be a single letter or digit).
Return: In the function name: true, if ch is an operand, false
otherwise.

*/

bool IsOperand(char ch)
{
if (((ch >= 'a') && (ch <= 'z')) ||
((ch >= 'A') && (ch <= 'Z')) ||
((ch >= '0') && (ch <= '9')))
return true;
else
return false;
}

/* Given:
OperatorA A character representing an operator or
parenthesis.
OperatorB A character representing an operator or
parenthesis.
Task: To determine whether OperatorA takes precedence over OperatorB.

Return: In the function name: true, if OperatorA takes precedence
over OperatorB.
*/
bool TakesPrecedence(char OperatorA, char OperatorB)
{
if (OperatorA == '(')
return false;
else if (OperatorB == '(')
return false;
else if (OperatorB == ')')
return true;
else if ((OperatorA == '^') && (OperatorB == '^'))
return false;
else if (OperatorA == '^')
return true;
else if (OperatorB == '^')
return false;
else if ((OperatorA == '*') || (OperatorA == '/'))
return true;
else if ((OperatorB == '*') || (OperatorB == '/'))
return false;
else
return true;

}

/* Given: Infix A string representing an infix expression (no spaces).
Task: To find the postfix equivalent of this expression.
Return: Postfix A string holding this postfix equivalent.
*/

void Convert(const string & Infix, string & Postfix)
{
stack<char> OperatorStack;
char TopSymbol, Symbol;
int k;
for (k = 0; k < Infix.size(); k++)
{
Symbol = Infix[k];
if (IsOperand(Symbol))
Postfix = Postfix + Symbol;
else
{
while ((! OperatorStack.empty()) &&
(TakesPrecedence(OperatorStack.top(), Symbol)))
{
TopSymbol = OperatorStack.top();
OperatorStack.pop();
Postfix = Postfix + TopSymbol;
}
if ((! OperatorStack.empty()) && (Symbol == ')'))
OperatorStack.pop(); // discard matching (
else
OperatorStack.push(Symbol);
}
}
while (! OperatorStack.empty())
{
TopSymbol = OperatorStack.top();
OperatorStack.pop();
Postfix = Postfix + TopSymbol;
}
}