/*	#define DEBUG		*/
/*To study how this program works trace F7 after defining DEBUG*/
/*or just remove the comment part "/ * * /" on the first line */

/* * * * * * * * * * * * * * * * * * * *  * * * * * * * * * * * * * * * * * *
*                                                                           *
*	Palindrome without the help of "string.h" library functions         *
*                                                                           *
*			-- Author Rajesh _ThE gReAt                         *
*                                                                           *
* * * * * * * * * * * * * * * * * * * *  * * * * * * * * * * * * * * * * * */

#include<stdio.h>
#include<dos.h>
#include<conio.h>
#include<math.h>
#include<string.h>
#include<ctype.h>
#include<graphics.h>
#include<stdlib.h>

#ifdef DEBUG
	int gl_fl;
#endif

main()
{
	char string[20];
	char rev[20];
	clrscr();
	printf("\nPlease enter a string\t");
	scanf("%s",string);
	copystr(rev,string);
	revstr(rev);
#ifdef DEBUG
	printf("\nReversed string is \"%s\"",rev);
#endif
	if(!compare(rev,string))
		printf("\nVoila ... ! a palindrome");
	else
		printf("\nNot a palindrome..");
#ifdef DEBUG
	printf("\ngl_fl = %d",gl_fl);
#endif
	getch();
}
copystr(char *dest,char *src)
{
	while((*(dest++)=*(src++)) != 0);
}
revstr(char str[20])
{
	char ch;
	int stlen=0,i=0,cstlen;
#ifdef DEBUG
	int ite=0;
	printf("\nControl transferred to revstr");
	fflush(stdout);
#endif
	stlen=length(str);
	cstlen=--stlen;
#ifdef DEBUG
	printf("\ncstlen = %d\nstlen=%d",cstlen,stlen);
#endif
	while(cstlen!=(stlen/2))
	{
		if(cstlen==i)
			break;
		ch=str[cstlen];
		str[cstlen]=str[i];
		str[i]=ch;
		cstlen--;
		i++;
#ifdef DEBUG
	ite++;
	printf("\nIteration no %d value of i = %d value of stlen = %d string is %s\nch=%c",ite,i-1,cstlen+1,str,ch);
#endif
	}
}
compare(char *str1,char *str2)
{
	short fl,i=0;
#ifdef DEBUG
	printf("\ntransfer passed to comapre()");
#endif
	while(i<length(str1) && i<length(str2))	 /*Though length(str1)==lenght(str2) to make this a general pupose function, both are tested*/
	{
		if((*str1==0 || *str2==0) && !(*str1==0 && *str2==0))
		{
#ifdef DEBUG
	gl_fl=1;
#endif
			return 1;
		}
		else if(*str1==0 || *str2==0)
		{
#ifdef DEBUG
	gl_fl=4;
#endif
			return fl;
		}
		else if(str1[i]==str2[i])
		{
#ifdef DEBUG
	gl_fl=2;
#endif
			fl=0;
		}
		else if((str1[i]>='A' && str1[i]<='Z') && ((str1[i]+32)==str2[i]))
		{
#ifdef DEBUG
	gl_fl=2;
#endif
			fl=0;
		}
		else if((str1[i]>='a' && str1[i]<='z') && ((str1[i]-32)==str2[i]))
		{
#ifdef DEBUG
	gl_fl=2;
#endif
			fl=0;
		}
		else
		{
#ifdef DEBUG
	gl_fl=3;
#endif
			return 1;
		}
		i++;

	}
	return fl;
}

length(char *work)
{
	int stlen=0;
	while(*(work++))
		stlen++;
	return stlen;
}