//Name   : Pratik Patel
//Roll No: 02CE048
//Subject: DSA
//Program: To convert an eq into postfix including (,)

#include <stdio.h>
#include <conio.h>

void main()
{
	clrscr();
	char eq[50];
	int i,j=0;
	char temp[50],answer[50];
	int tos=0,prev_prec,prec;
	printf("\nEnter the Expression: ");
	scanf("%s",eq);
	temp[0]=eq[0];
	tos++;
	if(eq[0]>='a'&&eq[0]<='z')
	{
		prev_prec=1;
	}
	else if(eq[0]=='(')
	{
		prev_prec=10;
	}
	for(i=1;eq[i]!='\0';i++)
	{
	   if (eq[i]==')')
	   {
		prec=9;
	   }
	   else if(eq[i]=='(')
	   {
		prec=10;
	   }
	   else if(eq[i]=='+'||eq[i]=='-')
	   {
			prec=3;
	   }
	   else if(eq[i]=='*'||eq[i]=='/')
	   {
			prec=2;
	   }
	   else if(eq[i]>='a'&&eq[i]<='z')
	   {
			prec=1;
	   }
check:
	   if(prec<prev_prec||prec==10)
	   {
			temp[tos]=eq[i];
			tos++;
			prev_prec=prec;
		}
		else
		{
			tos--;
			answer[j]=temp[tos];
			j++;
			if(tos==0)
			{
				temp[tos]=eq[i];
				prev_prec=prec;
				tos++;
			}
			else
			{
			tos--;
			setprec: if(temp[tos]=='+'||temp[tos]=='-')
			{
				prev_prec=3;
			}
			else if(temp[tos]=='*'||temp[tos]=='/')
			{
				prev_prec=2;
			}
			else if(temp[tos]>='a'&&temp[tos]<='z')
			{
				prev_prec=1;
			}
			else if(temp[tos]=='(')
			{
				if(prec==9)
				{
					tos--;
					if(temp[tos]>='a'&&temp[tos]<='z')
					{
						prev_prec=1;
					}
					else if(temp[tos]=='+'||temp[tos]=='-')
					{
						prev_prec=3;
					}
					else if(temp[tos]=='*'||temp[tos]=='/')
					{
						prev_prec=2;
					}
					else if(temp[tos]=='(')
					{
						prev_prec=10;
					}
				}
				prev_prec=10;
			}
			else if(temp[tos]==')')
			{
				prev_prec=9;
			}
			tos++;
			goto check;
			}
		 }
	}
	tos--;
	for(i=tos;i>=0;i--)
	{
		answer[j]=temp[i];
		j++;
	}
	answer[j]='\0';
	printf("\n");
	for(i=0;answer[i]!='\0';i++)
	{
		if(answer[i]=='('||answer[i]==')')
		{}
		else
		printf("%c",answer[i]);
	}
	getch();
}
/*
OUTPUT
Enter the infix expression:(((a-(b/c))-(d*e))+f)
abc/-de*-f+
*/