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infixtoprefix.cpp
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#include<iostream>
#include<stack>
using namespace std;
class infix
{
string exp;
stack<char>ch;
public:
void read();
int isoperator(char c);
int higherprecidence(char c,char p);
void infixtopostfix(string &s);
int isoperand(char c);
int pre(char p);
};
void infix::infixtopostfix(string &s)
{
string postfix =" ";
for(int i=0;i<s.length();i++)
{
if(isoperand(s[i]))
{
postfix = postfix+s[i];
}
else
if(isoperator(s[i]))
{
while(!ch.empty() && higherprecidence(ch.top(),s[i]))
{
postfix = postfix+ch.top();
ch.pop();
}
ch.push(s[i]);
}
else
if(s[i] == '(')
{
ch.push(s[i]);
}
else
if(s[i]==')')
{
while(!ch.empty()&& ch.top()!='(')
{
postfix+= ch.top();
ch.pop();
}
ch.pop();
}
}
while(!ch.empty())
{
postfix+=ch.top();
ch.pop();
}
cout<<postfix;
}
void infix::read()
{
cout<<"enter the string"<<endl;
cin>>exp;
infixtopostfix(exp);
}
int infix::isoperator(char ch)
{
if(ch=='+'|| ch =='-'||ch=='*'||ch=='/')
{
return true;
}
else
{
return false;
}
}
int infix::isoperand(char ch)
{
if(ch >='a' && ch<='z')return true;
else
if(ch >='0' && ch<='9')return true;
else
if(ch >='A' && ch <= 'Z' )return true;
else
return false;
}
int infix::higherprecidence( char ch , char p)
{
int op1 = pre(ch);
int op2 = pre(p);
if(op1>op2)
{
return true;
}
else
{
return false;
}
}
int infix::pre(char p)
{
int pre = -1;
switch(p)
{
case '+':
case '-': pre = 1;
break;
case '*':
case '/': pre = 2;
break;
case '^':pre = 3;
}
return pre;
}
int main()
{
infix a;
a.read();
}