Infix to Postfix
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/*
Infix to Postfix Conversion
- Converts an Infix(Inorder) expression to Postfix(Postorder)
- For eg. '1*2+3' converts to '12*3+'
- Valid Operators are +,-,*,/
- No Error Handling in this version
JavaScript Implementation
- CopyRight 2002 Premshree Pillai
See algorithm at
-http://www.qiksearch.com/articles/cs/infix-postfix/index.htm
Created : 28/08/02 (dd/mm/yy)
Web : http://www.qiksearch.com
E-mail : qiksearch@rediffmail.com
*/
function push_stack(stackArr,ele)
{
stackArr[stackArr.length]=ele;
}
function pop_stack(stackArr)
{
var _temp=stackArr[stackArr.length-1];
delete stackArr[stackArr.length-1];
stackArr.length--;
return(_temp);
}
function isOperand(who)
{
return(!isOperator(who)? true : false);
}
function isOperator(who)
{
return((who=="+" || who=="-" || who=="*" || who=="/" || who=="(" || who==")")? true : false);
}
function topStack(stackArr)
{
return(stackArr[stackArr.length-1]);
}
function isEmpty(stackArr)
{
return((stackArr.length==0)? true : false);
}
/* Check for Precedence */
function prcd(char1,char2)
{
var char1_index,char2_index;
var _def_prcd="-+*/";
for(var i=0; i<_def_prcd.length; i++)
{
if(char1==_def_prcd.charAt(i)) char1_index=i;
if(char2==_def_prcd.charAt(i)) char2_index=i;
}
if(((char1_index==0)||(char1_index==1)) && (char2_index>1)) return false;
else return true;
}
function InfixToPostfix(infixStr,postfixStr)
{
var postfixStr=new Array();
var stackArr=new Array();
var postfixPtr=0;
infixStr=infixStr.split('');
for(var i=0; i
if(isOperand(infixStr[i]))
{
postfixStr[postfixPtr]=infixStr[i];
postfixPtr++;
}
else
{
while((!isEmpty(stackArr)) && (prcd(topStack(stackArr),infixStr[i])))
{
postfixStr[postfixPtr]=topStack(stackArr);
pop_stack(stackArr);
postfixPtr++;
}
if((!isEmpty(stackArr)) && (infixStr[i]==")"))
{
pop_stack(stackArr);
}
else
{
push_stack(stackArr,infixStr[i]);
}
}
}
while(!isEmpty(stackArr))
{
postfixStr[postfixStr.length]=topStack(stackArr);
pop_stack(stackArr);
}
var returnVal='';
for(var i=0; i
returnVal+=postfixStr[i];
}
return(returnVal);
}
Infix to Postfix Conversion
Infix Expression :
Postfix Expression :
This is the "JavaScript" Implementation of converting an Infix(Inorder) expression to Postfix(Postorder) expression.
Click here for the algorithm used.
© 2002 Premshree Pillai.