11-23-2010, 05:01 AM
IDEA Solution of cs301 second assignment
Code:
#include<iostream.h>
#include<string.h>
#include<stdlib.h>
#include<ctype.h>
class expression
{
private:
char infix[100];
char stack[200];
int top;
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(c)!=0)
return 7;
else if(c==’(‘)
return 9;
else if(c==’)')
return 0;
else
{
cout<<”Invalid expression ::input error\n”;
exit(0);
}
}
int expression::stack_p(char c)
{
if(c==’+’ || c==’-')
return 2;
else if(c==’*’ || c==’/')
return 4;
else if(c==’^')
return 5;
else if(isalpha(c)!=0)
return 8;
else if(c==’(‘)
return 0;
else
{
cout<<”Invalid expression ::stack 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(c)!=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
top=1;
stack[top]=’(‘;
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[top]) )
{
if(top<1)
{
cout<<”invalid expression ::stack error\n”;
exit(0);
}
postfix[++x]=stack[top];
top–;
r=r+rank(postfix[x]);
if(r<1)
{
cout<<”Invalid expression ::r<1\n”;
exit(0);
}
}
if(input_p( next ) != stack_p( stack[top]))
stack[++top]=next;
else
top–;
i++;
next=infix[i];
}
postfix[++x]=”;
if(r!=1 || top!=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;