Assignment : Data structure
Conversion of infix expression to postfix expression
#include”stdio.h”
#include “stdafx.h”
#include”conio.h”
#include”iostream”
#include”stdlib.h”
#include”string.h”
using namespace std;
# define MAX 100
int top=-1;
char infix[100],postfix[100];
char stack[100];
int priority(char symbol)
{
switch(symbol)
{
case ‘(‘:return 0;
case ‘+’:
case ‘-‘:
return 1;
case ‘/’:
case ‘*’:
case ‘%’:
return 2;
case ‘^’:
return 3;
default :return 0;
}
}
void push(char symbol)
{
if(top==MAX-1)
{
cout<<“Stack overflow:\n”;
exit(1);
}
top=top+1;
stack[top]=symbol;
}
char pop()
{
if(top==-1)
{
cout<<“Stack underflow:\n”;
exit(1);
}
return stack[top–];
}
void infix_to_postfix()
{
int i,p=0;
char symbol,next;
for(i=0;i<strlen(infix);i++)
{
symbol=infix[i];
switch(symbol)
{
case ‘(‘:push(symbol);
break;
case ‘)’:while((next=pop())!='(‘)
{
postfix[p]=next;
p++;
}
break;
case ‘+’:
case ‘-‘:
case ‘*’:
case ‘/’:
case ‘%’:
case ‘^’:
while(top!=-1 && priority(stack[top])>=priority(symbol))
{//or stack is empty
postfix[p]=pop();
p++;
}
push(symbol);
break;
default://if operand comes
postfix[p]=symbol;
p++;
}
}
while(top!=-1)
{
postfix[p]=pop();
//printf(“%c”,pop());
p++;
}
postfix[p]=’\0′;
}
int main()
{
cout<<“Enter the infix expression:\n”;
cin>>infix;
cout<<“The post fix expression is:\n”;
infix_to_postfix();
printf(“-> %s”,postfix);
getch();
return 0;
}
