infix to postfix best algorithm

Infix to postfix best algorithm

Code:

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

int priority(char);

void main()
{
	int i=0,j=0,len,sp=0,p1,p;
	char infix[50],postfix[50],oprstack[45];
	clrscr();
	printf("enter the infix expression\n");
	scanf("%s",infix);
	len=strlen(infix);
	oprstack[sp]='(';
	infix[len]=')';
	infix[len+1]='\0';
	printf("%s",infix);

	while(infix[i]!='\0')
	{
		if(isdigit(infix[i]) || isalpha(infix[i]))
			postfix[j++]=infix[i];
		else if(infix[i]=='(')
		{
			sp++;
			oprstack[sp]=infix[i];
		}
		else if(infix[i]==')')
		{
			while(oprstack[sp]!='(')
			{
				postfix[j++]=oprstack[sp];
				sp--;
			}
			sp--;
		}
		else
			while(1)
			{
				p=priority(infix[i]);
				p1=priority(oprstack[sp]);
				if(p<=p1 && oprstack[sp]!='(')
				{
					postfix[j++]=oprstack[sp];
					sp--;
				}
				else
				{
					sp++;
					oprstack[sp]=infix[i];
					break;
				}
			}
			
			i++;
	}
	postfix[j]=0;
	printf("\nthe postfix expression is %s",postfix);
	getch();
}
int priority(char ch)
{
	int k;
	if(ch=='+' || ch=='-' )
		k=1;
	else if(ch=='*' || ch=='/' )
		k=2;
	else
		k=0;
	return k;
}

undefined