PROGRAM TO DEMONSTRATE THE USE OF STACK (IMPLEMENTED USING LINEAR ARRAY IN CONVERTING ARITHMETIC EXPRESSION FROM INFIX TO POSTFIX NOTATION.

Here is the program :

#include<iostream.h>

#include<conio.h>

#define SIZE 50

#include<ctype.h>

char s[SIZE];

int top=-1;

push(char elem)

{

            s[++top]=elem;

}

char pop()

{

            return(s[top--]);

}

int pr(char elem)

{ 

            switch(elem)

            {

            case'#':

return 0;

            case'(':

            return 1;

            case'+':

            case'-':

            return 2;

            case'*':

            case'/':

            return 3;

            case'^':

            return 4;

            }

            }

            void main()

            {

            char infx[50],pofx[50],ch,elem;

            int i=0,k=0;

            clrscr();

            cout<<"Read the infix expressionn?\n\n\t Enter Expression:";

            cin>>infx;

            push('#');

            while((ch=infx[i++])!='\0')

            {

            if(ch=='(')

            push(ch);

            else if(isalnum(ch))

            pofx[k++]=ch;

            else if(ch==')')

            {

            while(s[top]!='(')

            pofx[k++]=pop();

            elem=pop();

            }

            else

            {

            while(pr(s[top])>=pr(ch))

            pofx[k++]=pop();

            push(ch);

            }

            }

            while(s[top]!='#')

            pofx[k++]=pop();

            pofx[k]='\0';

            cout<<"\n\tPostfix="<<pofx;

            getch();

            }

Output is :