CS301 Data Structures assignment no 1 spring 25 October 2011

[makyle]

#include<iostream.h>
#include<string.h>
#include<stdlib.h>
#include<ctype.h>
class expression
{
private:
char infix[100];
char stack[200];
int first;
int r;
char postfix[100];
public:
void convert();
int input_p(char);
int stack_p(char);
int rank(char);
};
int expression::input_p(char c)
{
if(c=='+' || c=='-')
return 1;
else if(c=='*' || c=='/')
return 3;
else if(c=='^')
return 6;
else if(isalpha©!=0)
return 7;
else if(c=='(')
return 9;
else if(c==')')
return 0;
else
{
cout<<"Invalid expression ::input error\n";
exit(0);
}
}
int expression:tack_p(char c)
{
if(c=='+' || c=='-')
return 2;
else if(c=='*' || c=='/')
return 4;
else if(c=='^')
return 5;
else if(isalpha©!=0)
return 8;
else if(c=='(')
return 0;
else
{
cout<<"Invalid expression :tack error\n";
exit(0);
}
}
int expression::rank(char c)
{
if(c=='+' || c=='-')
return -1;
else if(c=='*' || c=='/')
return -1;
else if(c=='^')
return -1;
else if(isalpha©!=0)
return 1;
else
{
cout<<"Invalid expression ::in rank\n";
exit(0);
}
}
void expression::convert()
{
cout<<"\n*************************************************\n"
<<"This program converts the given infix expression\n"
<<"in to postfix form"
<<"\n*************************************************\n";
cout<<"Enter an infix expression ::\n";
cin>>infix;
int l=strlen(infix);
infix[l]=')';
infix[l+1]=";
//Convertion starts
first=1;
stack[first]='(';
r=0;
int x=-1;
int i=0;
char next=infix[i];
while(next!=")
{
//Pop all the elements to outputin stack which have higher precedence
while( input_p(next) < stack_p(stack[first]) )
{
if(first<1)
{
cout<<"invalid expression :tack error\n";
exit(0);
}
postfix[++x]=stack[first];
first-;
r=r+rank(postfix[x]);

if(r<1)
{
cout<<"Invalid expression ::r<1\n";
exit(0);
}
}
if(input_p( next ) != stack_p( stack[first]))
stack[++first]=next;
else
first-;
i++;
next=infix[i];
}
postfix[++x]=";
if(r!=1 || first!=0)
{
cout<<"Invalid expression ::error in rank or stack\n";
exit(0);
}
cout<<"\n\nThe corresponding postfix expression is ::\n";
cout<<postfix<<endl;
}
int main()
{
expression obj;
obj.convert();
return 0;